Arindam Bhadra

Distributing Video Over CAT 5 and CAT 7

2011-12-13T00:40:00.000+05:30

Some SI Need to Know About Video Distribution Through Cat5 or Cat7

When thinking of setting up your home video system, it means that you should know something about distributing video over CAT5 and CAT7 because it is the kind of system that will broadcast optimum performance. It also means that you can now have your source from a distance away from the display device, television or monitor.
There are three (3) general types of video distribution system:
1) Analog or Baseband
2) Internet Protocol
3) Radio Frequency

Any of these types may use coaxial cables, category 5 or more commonly known as CAT5 cables, CAT5e, CAT6, CAT6e or CAT7 cables. What are the differences between them?
1) CAT-5 distributes video up to 100M.
2) CAT-5e 350M.
3) CAT-6 and CAT6e distributes video as far as 550M to 1000M
4) CAT-7 is rated from 700M to 1000M.

Viewing Video Over CAT5 or CAT7
Video over CAT5 or CAT7 like those delivered by CATV, data, and telephone are all distributed in similar wiring closets. It delivers videos that may run along a distance of 100M for CAT 5 or even up to 1000M for CAT7. Video over CAT5 or CAT7 all goes out on the same cabling system. The system is channeled in a passive broadband balun that converts any uneven coaxial signal into a balanced signal through the video over CAT5 or CAT7. Even when distributed to different channels simultaneously, it will not slow down the network because the air analog signals do not travel on that similar network, and thus, it does not rely on the bandwidth of the video signals.
Presently, the use of FTP or UTP cables for audio and video needs is prevalent. Instead of using coaxial cables, CAT5 and CAT7 cables are used. Coax are first installed into the hubs and everything else is distributed through the FTP/UTP. Video over CAT7 or CAT5 for that matter are now possible at a limited cost. There is ease in the installation and location change is not a big deal. All one needs to do is connect patch cords from the distribution hub to the patch panel and have a single port converter connected to the television.

Advantages of a Video System Using CAT5 and CAT7
1) Video over CAT5 or CAT7 is cost effective as it eliminates the need for additional coaxial cables.
2) Configuration of video over CAT5 or CAT7 is much easier than having multiple splitter taps, amplifiers and combiners of coax.
3) A high quality signal is maintained as the distribution system of video over CAT5 or video over CAT7 uses active RF video hubs. It makes automatic slope adjustments hence all video channels’ image quality is sustained.
4) The video distribution system of CAT5 or CAT7 can carry out voice and auxiliary signals simultaneously. There are no interferences between the voice and video data.
5) A system with video over CAT5 or CAT7 allows video streaming from the computer and it is made possible through a broadband video system.
Distributing video over CAT5 and CAT7 is made possible through an RF broadband system. It broadcasts CATV, HDTV, internally generated video, video-on-demand services, and satellite videos through twisted pairs of CAT5 or CAT7 cables.

Details of PAL & NTSC Streaming

2011-12-13T00:16:00.002+05:30

PAL

PAL, short for Phase Alternating Line, is an analogue television colour encoding system used in broadcast television systems in many countries. Other common analogue television systems are NTSC and SECAM. This page primarily discusses the PAL colour encoding system. The articles on broadcast television systems and analogue television further describe frame rates, image resolution and audio modulation. For discussion of the 625-line / 50 field (25 frame) per second television standard.

History
In the 1950s, the Western European countries commenced planning to introduce colour television, and were faced with the problem that the NTSC standard demonstrated several weaknesses, including colour tone shifting under poor transmission conditions. To overcome NTSC's shortcomings, alternative standards were devised, resulting in the development of the PAL and SECAM standards. The goal was to provide a colour TV standard for the European picture frequency of 50 fields per second (50 hertz), and finding a way to eliminate the problems with NTSC.

PAL was developed by Walter Bruch at Telefunken in Germany. The format was unveiled in 1963, with the first broadcasts beginning in the United Kingdom in 1964 and Germany in 1967, though the one BBC channel initially using the broadcast standard only began to broadcast in colour from 1967.

Telefunken was later bought by the French electronics manufacturer Thomson. Thomson also bought the Compagnie Générale de Télévision where Henri de France developed SECAM, the first European Standard for colour television. Thomson, now called Technicolor SA, also owns the RCA brand and licenses it to other companies; Radio Corporation of America, the originator of that brand, created the NTSC colour TV standard before Thomson became involved.
The term PAL is often used informally to refer to a 625-line/50 Hz (576i) television system, and to differentiate from a 525-line/60 Hz (480i) NTSC system. Accordingly, DVDs are labeled as either PAL or NTSC (referring informally to the line count and frame rate) even though technically the discs do not have either PAL or NTSC composite colour. The line count and frame rate are defined as EIA 525/60 or CCIR 625/50. PAL and NTSC are only the method of colour transmission.
Colour encoding
Both the PAL and the NTSC system use a quadrature amplitude modulated subcarrier carrying the chrominance information added to the luminance video signal to form a composite video baseband signal. The frequency of this subcarrier is 4.43361875 MHz for PAL, compared to 3.579545 MHz for NTSC. The SECAM system, on the other hand, uses a frequency modulation scheme on its two line alternate colour subcarrier 4.25000 and 4.40625 MHz.

The name "Phase Alternating Line" describes the way that the phase of part of the colour information on the video signal is reversed with each line, which automatically corrects phase errors in the transmission of the signal by canceling them out, at the expense of vertical frame colour resolution. Lines where the colour phase is reversed compared to NTSC are often called PAL or phase-alternation lines, which justifies one of the expansions of the acronym, while the other lines are called NTSC lines. Early PAL receivers relied on the human eye to do that canceling; however, this resulted in a comb-like effect known as Hanover bars on larger phase errors. Thus, most receivers now use a chrominance delay line, which stores the received colour information on each line of display; an average of the colour information from the previous line and the current line is then used to drive the picture tube. The effect is that phase errors result in saturation changes, which are less objectionable than the equivalent hue changes of NTSC. A minor drawback is that the vertical colour resolution is poorer than the NTSC system's, but since the human eye also has a colour resolution that is much lower than its brightness resolution, this effect is not visible. In any case, NTSC, PAL, and SECAM all have chrominance bandwidth (horizontal colour detail) reduced greatly compared to the luminance signal.

The 4.43361875 MHz frequency of the colour carrier is a result of 283.75 colour clock cycles per line plus a 25 Hz offset to avoid interferences. Since the line frequency (number of lines per second) is 15625 Hz (625 lines x 50 Hz / 2), the colour carrier frequency calculates as follows: 4.43361875 MHz = 283.75 * 15625 Hz + 25 Hz.

The original colour carrier is required by the colour decoder to recreate the colour difference signals. Since the carrier is not transmitted with the video information it has to be generated locally in the receiver. In order that the phase of this locally generated signal can match the transmitted information, a 10 cycle burst of colour subcarrier is added to the video signal shortly after the line sync pulse, but before the picture information, during the so called back porch. This colour burst is not actually in phase with the original colour subcarrier, but leads it by 45 degrees on the odd lines and lags it by 45 degrees on the even lines. This swinging burst enables the colour decoder circuitry to distinguish the phase of the R-Y vector which reverses every line.
PAL vs. NTSC
NTSC receivers have a tint control to perform colour correction manually. If this is not adjusted correctly, the colors may be faulty. The PAL standard automatically cancels hue errors by phase reversal, so a tint control is unnecessary. Chrominance phase errors in the PAL system are cancelled out using a 1H delay line resulting in lower saturation, which is much less noticeable to the eye than NTSC hue errors.

However, the alternation of colour information — Hanover bars — can lead to picture grain on pictures with extreme phase errors even in PAL systems, if decoder circuits are misaligned or use the simplified decoders of early designs (typically to overcome royalty restrictions). In most cases such extreme phase shifts do not occur. This effect will usually be observed when the transmission path is poor, typically in built up areas or where the terrain is unfavorable. The effect is more noticeable on UHF than VHF signals as VHF signals tend to be more robust.

In the early 1970s some Japanese set manufacturers developed decoding systems to avoid paying royalties to Telefunken. The Telefunken license covered any decoding method that relied on the alternating subcarrier phase to reduce phase errors. This included very basic PAL decoders that relied on the human eye to average out the odd/even line phase errors. One solution was to use a 1H delay line to allow decoding of only the odd or even lines. For example, the chrominance on odd lines would be switched directly through to the decoder and also be stored in the delay line. Then, on even lines, the stored odd line would be decoded again. This method effectively converted PAL to NTSC. Such systems suffered hue errors and other problems inherent in NTSC and required the addition of a manual hue control.

PAL and NTSC have slightly divergent color spaces, but the colour decoder differences here are ignored.
PAL vs. SECAM
SECAM is an earlier attempt at compatible colour television which also tries to resolve the NTSC hue problem. It does so by applying a different method to colour transmission, namely alternate transmission of the U and V vectors and frequency modulation, while PAL attempts to improve on the NTSC method.
SECAM transmissions are more robust over longer distances than NTSC or PAL. However, owing to their FM nature, the colour signal remains present, although at reduced amplitude, even in monochrome portions of the image, thus being subject to stronger cross colour. Like PAL, a SECAM receiver needs a delay line.

PAL signal details

For PAL-B/G the signal has these characteristics.

Parameter	Value
Pixel Clock frequency (digital sources with 704 or 720 active Pixel/Line)	13.5 MHz
Bandwidth	5 MHz
Horizontal sync polarity	Negative
Total time for each line	64.000 µs
Front porch (A)	1.65+0.4 −0.1 µs
Sync pulse length (B)	4.7±0.20 µs
Back porch (C)	5.7±0.20 µs
Active video (D)	51.95+0.4 −0.1 µs

(Total horizontal sync time 12.05 µs)

After 0.9 µs a 2.25±0.23 µs color burst of 10±1 cycles is sent. Most rise/fall times are in 250±50 ns range. Amplitude is 100% for white level, 30% for black, and 0% for sync. The CVBS electrical amplitude is Vpp 1.0 V and impedance of 75 Ω.

The composite video (CVBS) signal used in systems M and N before combination with a sound carrier and modulation onto an RF carrier.

The vertical timings are:

Parameter	Value
Vertical lines	313 (625 total)
Vertical lines visible	288 (576 total)
Vertical sync polarity	Negative (burst)
Vertical frequency	50 Hz
Sync pulse length (F)	0.576 ms (burst)
Active video (H)	18.4 ms

As PAL is interlaced, every two fields are summed to make a complete picture frame.

Luminance, Y, is derived from red, green, and blue (R'G'B') signals:

Y = 0.299R' + 0.587G' + 0.114B'

U and V are used to transmit chrominance. Each has a typical bandwidth of 1.3 MHz.

$U = 0.492(B' - Y)$
$V = 0.877(R' - Y)$

Composite PAL signal

= Y + U sin(ω t) + V cos(ω t) +

timing where

ω = 2π F SC

Subcarrier frequency

F SC

is 4.43361875 MHz (±5 Hz) for PAL-B/D/G/H/I/N.

PAL broadcast systems

This table illustrates the differences:

	PAL B	PAL G, H	PAL I	PAL D/K	PAL M	PAL N
Transmission Band	VHF	UHF	UHF/VHF*	VHF/UHF	VHF/UHF	VHF/UHF
Fields	50	50	50	50	60	50
Lines	625	625	625	625	525	625
Active lines	576	576	582**	576	480	576
Channel Bandwidth	7 MHz	8 MHz	8 MHz	8 MHz	6 MHz	6 MHz
Video Bandwidth	5.0 MHz	5.0 MHz	5.5 MHz	6.0 MHz	4.2 MHz	4.2 MHz
Colour Subcarrier	4.43361875 MHz	4.43361875 MHz	4.43361875 MHz	4.43361875 MHz	3.575611 MHz	3.58205625 MHz
Sound Carrier	5.5 MHz	5.5 MHz	6.0 MHz	6.5 MHz	4.5 MHz	4.5 MHz

* System I has never been used on VHF in the UK.
** The UK's adoption of 582 active lines has no significant impact on either non system I receivers or non system I source material as the extra lines are not within the normal display area and do not contain anything in the other standards anyway. All Digital TV broadcasts and digital recordings (e.g. DVDs) conform to the 576 active line standards.

PAL-B/G/D/K/I

The majority of countries using PAL have television standards with 625 lines and 25 frames per second, differences concern the audio carrier frequency and channel bandwidths. Standards B/G are used in most of Western Europe, Australia and New Zealand, standard I in the UK, Ireland, Hong Kong, South Africa and Macau, standards D/K in most of Central and Eastern Europe and Standard D in mainland China. Most analogue CCTV cameras are Standard D.

Systems B and G are similar. System B is used for 7 MHz-wide channels on VHF, while System G is used for 8 MHz-wide channels on UHF (and Australia uses System B on UHF). Similarly, Systems D and K are similar except for the bands they use: System D is only used on VHF, while System K is only used on UHF. Although System I is used on both bands, it has only been used on UHF in the United Kingdom due to 405-line TV services on VHF operating until the 1980s.

PAL-M (Brazil)

In Brazil, PAL is used in conjunction with the 525 line, 29.97 frame/s system M, using (very nearly) the NTSC colour subcarrier frequency. Exact colour subcarrier frequency of PAL-M is 3.575611 MHz. Almost all other countries using system M use NTSC.

The PAL colour system (either baseband or with any RF system, with the normal 4.43 MHz subcarrier unlike PAL-M) can also be applied to an NTSC-like 525-line (480i) picture to form what is often known as "PAL-60" (sometimes "PAL-60/525", "Quasi-PAL" or "Pseudo PAL"). PAL-M (a broadcast standard) however should not be confused with "PAL-60".

PAL-N (Argentina, Paraguay, Uruguay)

In Argentina, Paraguay and Uruguay the PAL-N variant is used. It employs the 625 line/50 field per second waveform of PAL-B/G, D/K, H, I, but on a 6MHz channel with a chrominance subcarrier frequency of 3.582 MHz very similar to NTSC.

VHS tapes recorded from a PAL-N or a PAL-B/G, D/K, H, I broadcast are indistinguishable because the down converted subcarrier on the tape is the same. A VHS recorded off TV (or released) in Europe will play in colour on any PAL-N VCR and PAL-N TV in Argentina, Paraguay, and Uruguay. Likewise, any tape recorded in Argentina or Uruguay off a PAL-N TV broadcast, can be sent to anyone in European countries that use PAL (and Australia/New Zealand, etc.) and it will display in colour. This will also play back successfully in Russia and other SECAM countries, as the USSR mandated PAL compatibility in 1985 - this has proved to be very convenient for video collectors.

People in Uruguay, Argentina and Paraguay usually own TV sets that also display NTSC-M, in addition to PAL-N. Direct TV also conveniently broadcasts in NTSC-M for North, Central and South America. Most DVD players sold in Argentina, Uruguay and Paraguay also play PAL discs - however, this is usually output in the European variant (colour subcarrier frequency 4.433618 MHz), so people who own a TV set which only works in PAL-N (plus NTSC-M in most cases) will have to watch those PAL DVD imports in black and white as the colour subcarrier frequency in the TV set is the PAL-N variation, 3.582056 MHz.

In the case that a VHS or DVD player works in PAL (and not in PAL-N) and the TV set works in PAL-N (and not in PAL), there are two options:

images can be seen in black and white, or
an inexpensive transcoder (PAL -> PAL-N) can be purchased in order to see the colors

Some DVD players (usually lesser known brands) include an internal transcoder and the signal can be output in NTSC-M, with some video quality loss due to the system's conversion from a 625/50 PAL DVD to the NTSC-M 525/60 output format. A few DVD players sold in Argentina, Uruguay and Paraguay also allow a signal output of NTSC-M, PAL, or PAL-N. In that case, a PAL disc (imported from Europe) can be played back on a PAL-N TV because there are no field/line conversions, quality is generally excellent.

Extended features of the PAL specification, such as Teletext, are implemented quite differently in PAL-N. PAL-N supports a modified 608 closed captioning format that is designed to ease compatibility with NTSC originated content carried on line 18, and a modified Teletext format that can occupy several lines.

PAL-L

The PAL L (Phase Alternating Line with L-sound system) standard uses the same video system as PAL-B/G/H (625 lines, 50 Hz field rate, 15.625 kHz line rate), but with 6 MHz video bandwidth rather than 5.5 MHz. This requires the audio subcarrier to be moved to 6.5 MHz. An 8 MHz channel spacing is used for PAL-L.

System A

The BBC tested their pre-war 405 line monochrome system with all three colour standards including PAL, before the decision was made to abandon 405 and transmit colour on 625/System I only.

PAL interoperability

The PAL colour system is usually used with a video format that has 625 lines per frame (576 visible lines, the rest being used for other information such as sync data and captioning) and a refresh rate of 50 interlaced fields per second (i.e. 25 full frames per second), such systems being B, G, H, I, and N (see broadcast television systems for the technical details of each format).

This ensures video interoperability. However as some of these standards (B/G/H, I and D/K) use different sound carriers (5.5MHz, 6.0MHz 6.5MHz respectively), it may result in a video image without audio when viewing a signal broadcast over the air or cable. Some countries in Eastern Europe which formerly used SECAM with systems D and K have switched to PAL while leaving other aspects of their video system the same, resulting in the different sound carrier. Instead, other European countries have changed completely from SECAM-D/K to PAL-B/G.

The PAL-N system has a different sound carrier, and also a different colour subcarrier, and decoding on incompatible PAL systems results in a black and white image without sound. The PAL-M system has a different sound carrier and a different colour subcarrier, and does not use 625 lines or 50 frames/second. This would result in no video or audio at all when viewing a European signal.

Multisystem PAL support and "PAL 60"

Recently manufactured PAL television receivers can typically decode all of these systems except, in some cases, PAL-M and PAL-N. Many of receivers can also receive Eastern European and Middle Eastern SECAM, though rarely French-broadcast SECAM (because France uses the unique positive video modulation) unless they are manufactured for the French market. They will correctly display plain CVBS or S-video SECAM signals. Many can also accept baseband NTSC-M, such as from a VCR or game console, and RF modulated NTSC with a PAL standard audio subcarrier (i.e. from a modulator), though not usually broadcast NTSC (as its 4.5 MHz audio subcarrier is not supported). Many sets also support NTSC with a 4.43 MHz subcarrier.

Many 1990s onwards VCR players sold in Europe can play back NTSC tapes/discs. When operating in this mode most of them do not output a true (625/25) PAL signal, but rather a hybrid consisting of the original NTSC line standard (525/30), but with colour converted to PAL 4.43 MHz - this is known as "PAL 60" (also "quasi-PAL" or "pseudo PAL") with "60" standing for 60 Hz (for 525/30), instead of 50 Hz (for 625/25). Some video game consoles also output a signal in this mode. Most newer television sets can display such a signal correctly, but some will only do so (if at all) in black and white and/or with flickering/foldover at the bottom of the picture, or picture rolling (however, many old TV sets can display the picture properly by means of adjusting the V-Hold and V-Height knobs — assuming they have them). Some TV tuner cards or video capture cards will support this mode (although software/driver modification can be required and the manufacturers' specs may be unclear). A "PAL 60" signal is similar to an NTSC (525/30) signal, but with the usual PAL chrominance subcarrier at 4.43 MHz (instead of 3.58 as with NTSC and South American PAL variants) and with the PAL-specific phase alternation of the red colour difference signal between the lines.

Most European DVD players output a true NTSC-M signal when playing NTSC discs, which many modern European TV sets can resolve.

Countries and territories using PAL

Over 120 countries and territories use or once used the terrestrial PAL system. Many of these are currently converting terrestrial PAL to DVB-T (PAL still often used by cable TV or in conjunction with a digital standard, such as DVB-C).

NTSC

NTSC, named for the National Television System Committee (NTSC), is the analog television system that is used in most of North America, most of South America (except Brazil, Argentina, Uruguay, and French Guiana), Burma, South Korea, Taiwan, Japan, the Philippines, and some Pacific island nations and territories.

Most countries using the NTSC standard, as well as those using other analog television standards, are switching to newer digital television standards, of which at least four different ones are in use around the world. North America, parts of Central America, and South Korea are adopting the ATSC standards, while other countries are adopting or have adopted other standards.

The first NTSC standard was developed in 1941 and had no provision for color television. In 1953 a second modified version of the NTSC standard was adopted, which allowed color television broadcasting compatible with the existing stock of black-and-white receivers. NTSC was the first widely adopted broadcast color system. After nearly 70 years of use, the vast majority of over-the-air NTSC transmissions in the United States was replaced with digital ATSC on June 12, 2009, and will be by August 31, 2011 in Canada and most other NTSC markets. Despite the shift to digital broadcasting, standard definition television in these countries continues to follow the NTSC standard in terms of frame rate and number of lines of resolution. In the United States a small number of short-range local and TV relay stations continue to broadcast NTSC, as the FCC allows. NTSC baseband video signals are also still often used in video playback (typically of recordings from existing libraries using existing equipment) and in CCTV and surveillance video systems.

History

The National Television System Committee was established in 1940 by the United States Federal Communications Commission (FCC) to resolve the conflicts that arose between companies over the introduction of a nationwide analog television system in the United States. In March 1941, the committee issued a technical standard for black-and-white television that built upon a 1936 recommendation made by the Radio Manufacturers Association (RMA). Technical advancements of the vestigial sideband technique allowed for the opportunity to increase the image resolution. The NTSC selected 525 scan lines as a compromise between RCA's 441-scan line standard (already being used by RCA's NBC TV network) and Philco's and DuMont's desire to increase the number of scan lines to between 605 and 800. The standard recommended a frame rate of 30 frames (images) per second, consisting of two interlaced fields per frame at 262.5 lines per field and 60 fields per second. Other standards in the final recommendation were an aspect ratio of 4:3, and frequency modulation (FM) for the sound signal.

In January 1950, the Committee was reconstituted to standardize color television. In December 1953, it unanimously approved what is now called the NTSC color television standard (later defined as RS-170a). The "compatible color" standard retained full backward compatibility with existing black-and-white television sets. Color information was added to the black-and-white image by adding a color subcarrier of 4.5 × 455/572 = 315/88 MHz (approximately 3.58 MHz) to the video signal. To reduce the visibility of interference between the chrominance signal and FM sound carrier required a slight reduction of the frame rate from 30 frames per second to 30/1.001 (approximately 29.97) frames per second, and changing the line frequency from 15,750 Hz to 15,750/1.001 Hz (approximately 15,734.26 Hz).

The FCC had briefly approved a different color television standard, starting in October 1950, which was developed by CBS. However, this standard was incompatible with black-and-white broadcasts. It used a rotating color wheel, reduced the number of scan lines from 525 to 405, and increased the field rate from 60 to 144, but had an effective frame rate of only 24 frames per second. Legal action by rival RCA kept commercial use of the system off the air until June 1951, and regular broadcasts only lasted a few months before manufacture of all color television sets was banned by the Office of Defense Mobilization (ODM) in October, ostensibly due to the Korean War. CBS rescinded its system in March 1953, and the FCC replaced it on December 17, 1953 with the NTSC color standard, which was cooperatively developed by several companies, including RCA and Philco.The first publicly announced network television broadcast of a program using the NTSC "compatible color" system was an episode of NBC's Kukla, Fran and Ollie on August 30, 1953, although it was viewable in color only at the network's headquarters. The first nationwide view of NTSC color came on the following January 1 with the coast-to-coast broadcast of the Tournament of Roses Parade, viewable on prototype color receivers at special presentations across the country.

The first color NTSC television camera was the RCA TK-40, used for experimental broadcasts in 1953; an improved version, the TK-40A, introduced in March 1954, was the first commercially available color television camera. Later that year, the improved TK-41 became the standard camera used throughout much of the 1960s.

The NTSC standard has been adopted by other countries, including most of the Americas and Japan. With the advent of digital television, analog broadcasts are being phased out. Most U.S. NTSC broadcasters were required by the FCC to shut down their analog transmitters in 2009. Low-power stations, Class A stations and translators were not immediately affected. An analog cut-off date for those stations was not set.

Technical details:

Lines and refresh rate

NTSC color encoding is used with the system M television signal, which consists of 29.97 interlaced frames of video per second, or the nearly identical system J in Japan. Each frame consists of a total of 525 scanlines, of which 486 make up the visible raster. The remainder (the vertical blanking interval) are used for synchronization and vertical retrace. This blanking interval was originally designed to simply blank the receiver's CRT to allow for the simple analog circuits and slow vertical retrace of early TV receivers. However, some of these lines now can contain other data such as closed captioning and vertical interval time code (VITC). In the complete raster (ignoring half-lines), the even-numbered or 'lower" scanlines (Every other line that would be even if counted in the video signal, e.g. {2,4,6,…,524}) are drawn in the first field, and the odd-numbered or "upper" (Every other line that would be odd if counted in the video signal, e.g. {1,3,5,….525}) are drawn in the second field, to yield a flicker-free image at the field refresh frequency of approximately 59.94 Hertz (actually 60 Hz/1.001). For comparison, 576i systems such as PAL-B/G and SECAM uses 625 lines (576 visible), and so have a higher vertical resolution, but a lower temporal resolution of 25 frames or 50 fields per second.

The NTSC field refresh frequency in the black-and-white system originally exactly matched the nominal 60 Hz frequency of alternating current power used in the United States. Matching the field refresh rate to the power source avoided intermodulation, which produces rolling bars on the screen. When color was later added to the system, the refresh frequency was shifted slightly downward to 59.94 Hz to eliminate stationary dot patterns in the difference frequency between the sound and color carriers, as explained below in “olor encoding” Synchronization of the refresh rate to the power incidentally helped kinescope cameras record early live television broadcasts, as it was very simple to synchronize a film camera to capture one frame of video on each film frame by using the alternating current frequency to set the speed of the synchronous AC motor-drive camera. By the time the frame rate changed to 29.97 Hz for color, it was nearly as easy to trigger the camera shutter from the video signal itself.

The actual figure of 525 lines was chosen as a consequence of the limitations of the vacuum-tube-based technologies of the day. In early TV systems, a master voltage-controlled oscillator was run at twice the horizontal line frequency, and this frequency was divided down by the number of lines used (in this case 525) to give the field frequency (60 Hz in this case). This frequency was then compared with the 60 Hz power-line frequency and any discrepancy corrected by adjusting the frequency of the master oscillator. For interlaced scanning, an odd number of lines per frame was required in order to make the vertical retrace distance identical for the odd and even fields, which meant the master oscillator frequency had to be divided down by an odd number. At the time, the only practical method of frequency division was the use of a chain of vacuum tube multivibrators, the overall division ratio being the mathematical product of the division ratios of the chain. Since all the factors of an odd number also have to be odd numbers, it follows that all the dividers in the chain also had to divide by odd numbers, and these had to be relatively small due the problems of thermal drift with vacuum tube devices. The closest practical sequence to 500 that meets these criteria was 3 × 5 × 5 × 7 = 525. (For the same reason, 625-line PAL-B/G and SECAM uses 5 × 5 × 5 × 5, the old British 405-line system used 3 × 3 × 3 × 3 × 5, the French 819-line system used 3 × 3 × 7 × 13 etc.).

Colorimetry

The original 1953 color NTSC specification, still part of the United States Code of Federal Regulations, defined the colorimetric values of the system as follows:

Original NTSC colorimetry (1953)	CIE 1931 x	CIE 1931 y
Primary red	0.67	0.33
Primary green	0.21	0.71
Primary blue	0.14	0.08
White point (CIE Standard illuminant C)	0.31	0.316

Early color television receivers, such as the RCA CT-100, were faithful to this specification, having a larger gamut than most of today's monitors. Their low-efficiency phosphors however were dark and long-persistent, leaving trails after moving objects. Starting in the late 1950s, picture tube phosphors would sacrifice saturation for increased brightness; this deviation from the standard both at the receiver and broadcaster ends was the source of considerable color variation.

Color correction in studio monitors and home receivers

To ensure more uniform color reproduction, receivers started to incorporate color correction circuits that converted the received signal — encoded for the colorimetric values listed above — into signals encoded for the phosphors actually used within the receiver.Since such color correction can not be performed accurately on the nonlinear (gamma-corrected) signals transmitted, the adjustment can only be approximated, introducing both hue and luminance errors for highly saturated colors.

Similarly at the broadcaster stage, in 1968-69 the Conrac Corp., working with RCA, defined a set of controlled phosphors for use in broadcast color picture video monitors.This specification survives today as the SMPTE "C" phosphor specification:

SMPTE "C" colorimetry	CIE 1931 x	CIE 1931 y
Primary red	0.63	0.34
Primary green	0.31	0.595
Primary blue	0.155	0.07
White point (CIE illuminant D65)	0.3127	0.329

As with home receivers, it was further recommended that studio monitors incorporate similar color correction circuits so that broadcasters would transmit pictures encoded for the original 1953 colorimetric values, in accordance with FCC standards.

In 1987, the Society of Motion Picture and Television Engineers (SMPTE) Committee on Television Technology, Working Group on Studio Monitor Colorimetry, adopted the SMPTE C (Conrac) phosphors for general use in Recommended Practice 145, prompting many manufacturers to modify their camera designs to directly encode for SMPTE "C" colorimetry without color correction., as approved in SMPTE standard 170M, "Composite Analog Video Signal — NTSC for Studio Applications" (1994). As a consequence, the ATSC digital television standard states that for 480i signals, SMPTE "C" colorimetry should be assumed unless colorimetric data is included in the transport stream.

Variations

Japanese NTSC uses the same colorimetric values for red, blue, and green, but employs a different white point of CIE Illuminant D93 (x=0.285, y=0.293). Both the PAL and SECAM systems used the original 1953 NTSC colorimetry as well until 1970; unlike NTSC, however, the European Broadcasting Union (EBU) eschewed color correction in receivers and studio monitors that year and instead explicitly called for all equipment to directly encode signals for the "EBU" colorimetric values, further improving the color fidelity of those systems.

Color encoding

For backward compatibility with black-and-white television, NTSC uses a luminance-chrominance encoding system invented in 1938 by Georges Valensi. Luminance (derived mathematically from the composite color signal) takes the place of the original monochrome signal. Chrominance carries color information. This allows black-and-white receivers to display NTSC signals simply by filtering out the chrominance. If it were not removed, the picture would be covered with dots (a result of chroma being interpreted as luminance). All black-and-white TVs sold in the US after the introduction of color broadcasting in 1953 were designed to filter chroma out, but the early B&W sets did not do this and chroma dots would show up in the picture.

In NTSC, chrominance is encoded using two 3.579545 MHz signals that are 90 degrees out of phase, known as I (in-phase) and Q (quadrature) QAM. These two signals are each amplitude modulated and then added together. The carrier is suppressed. Mathematically, the result can be viewed as a single sine wave with varying phase relative to a reference and varying amplitude. The phase represents the instantaneous color hue captured by a TV camera, and the amplitude represents the instantaneous color saturation.

For a TV to recover hue information from the I/Q phase, it must have a zero phase reference to replace the suppressed carrier. It also needs a reference for amplitude to recover the saturation information. So, the NTSC signal includes a short sample of this reference signal, known as the color burst, located on the 'back porch' of each horizontal line (the time between the end of the horizontal synchronization pulse and the end of the blanking pulse.) The color burst consists of a minimum of eight cycles of the unmodulated (fixed phase and amplitude) color subcarrier. The TV receiver has a "local oscillator", which it synchronizes to the color bursts and then uses as a reference for decoding the chrominance. By comparing the reference signal derived from color burst to the chrominance signal's amplitude and phase at a particular point in the raster scan, the device determines what chrominance to display at that point. Combining that with the amplitude of the luminance signal, the receiver calculates what color to make the point, i.e. the point at the instantaneous position of the continuously scanning beam. Note that analog TV is discrete in the vertical dimension (there are distinct lines) but continuous in the horizontal dimension (every point blends into the next with no boundaries), hence there are no pixels in analog TV. In CRT televisions, the NTSC signal is turned into RGB, which is then used to control the electron guns. Digital TV sets receiving analog signals instead convert the picture into discrete pixels. This process of discretization necessarily degrades the picture information somewhat, though with small enough pixels the effect may be imperceptible. Digital sets include all sets with a matrix of discrete pixels built into the display device, such as LCD, plasma, and DLP screens, but not CRTs, which do not have fixed pixels. This should not be confused with digital (ATSC) television signals, which are a form of MPEG video, but which still have to be converted into a format the TV can use.

When a transmitter broadcasts an NTSC signal, it amplitude-modulates a radio-frequency carrier with the NTSC signal just described, while it frequency-modulates a carrier 4.5 MHz higher with the audio signal. If non-linear distortion happens to the broadcast signal, the 3.579545 MHz color carrier may beat with the sound carrier to produce a dot pattern on the screen. To make the resulting pattern less noticeable, designers adjusted the original 60 Hz field rate down by a factor of 1.001 (0.1%), to approximately 59.94 fields per second. This adjustment ensures that the sums and differences of the sound carrier and the color subcarrier and their multiples (i.e., the intermodulation products of the two carriers) are not exact multiples of the frame rate, which is the necessary condition for the dots to remain stationary on the screen, making them most noticeable.

The 59.94 rate is derived from the following calculations. Designers chose to make the chrominance subcarrier frequency an n + 0.5 multiple of the line frequency to minimize interference between the luminance signal and the chrominance signal. (Another way this is often stated is that the color subcarrier frequency is an odd multiple of half the line frequency.) They then chose to make the audio subcarrier frequency an integer multiple of the line frequency to minimize visible (intermodulation) interference between the audio signal and the chrominance signal. The original black-and-white standard, with its 15750 Hz line frequency and 4.5 MHz audio subcarrier, does not meet these requirements, so designers had either to raise the audio subcarrier frequency or lower the line frequency. Raising the audio subcarrier frequency would prevent existing (black and white) receivers from properly tuning in the audio signal. Lowering the line frequency is comparatively innocuous, because the horizontal and vertical synchronization information in the NTSC signal allows a receiver to tolerate a substantial amount of variation in the line frequency. So the engineers chose the line frequency to be changed for the color standard. In the black-and-white standard, the ratio of audio subcarrier frequency to line frequency is 4.5 MHz / 15,750 = 285.71. In the color standard, this becomes rounded to the integer 286, which means the color standard's line rate is 4.5 MHz / 286 = approximately 15,734 lines per second. Maintaining the same number of scan lines per field (and frame), the lower line rate must yield a lower field rate. Dividing (4,500,000 / 286) lines per second by 262.5 lines per field gives approximately 59.94 fields per second.

Transmission modulation scheme

An NTSC television channel as transmitted occupies a total bandwidth of 6 MHz. The actual video signal, which is amplitude-modulated, is transmitted between 500 kHz and 5.45 MHz above the lower bound of the channel. The video carrier is 1.25 MHz above the lower bound of the channel. Like most AM signals, the video carrier generates two sidebands, one above the carrier and one below. The sidebands are each 4.2 MHz wide. The entire upper sideband is transmitted, but only 1.25 MHz of the lower sideband, known as a vestigial sideband, is transmitted. The color subcarrier, as noted above, is 3.579545 MHz above the video carrier, and is quadrature-amplitude-modulated with a suppressed carrier. The audio signal is frequency-modulated, like the audio signals broadcast by FM radio stations in the 88–108 MHz band, but with a ±25kHz maximum frequency swing, as opposed to ±75kHz as is used on the FM band. The main audio carrier is 4.5 MHz above the video carrier, making it 250 kHz below the top of the channel. Sometimes a channel may contain an MTS signal, which offers more than one audio signal by adding one or two subcarrier on the audio signal, each synchronized to a multiple of the line frequency. This is normally the case when stereo audio and/or second audio program signals are used. The same extensions are used in ATSC, where the ATSC digital carrier is broadcast at 1.31 MHz above the lower bound of the channel.

The Cvbs (Composite vertical blanking signal) (sometimes called "setup") is a voltage offset between the "black" and "blanking" levels. Cvbs is unique to NTSC. Cvbs has the advantage of making NTSC video more easily separated from its primary sync signals.

Framerate conversion

There is a large difference in frame rate between film, which runs at 24.0 frames per second, and the NTSC standard, which runs at approximately 29.97 frames per second.

Unlike the 576i video formats, this difference cannot be overcome by a simple speed-up.

A complex process called "3:2 pull down" is used. One film frame is transmitted for three video fields (1½ video frame times), and the next frame is transmitted for two video fields (one video frame time). Two film frames are therefore transmitted in five video fields, for an average of 2½ video fields per film frame. The average frame rate is thus 60 / 2.5 = 24 frame/s, so the average film speed is exactly what it should be. There are drawbacks, however. Still-framing on playback can display a video frame with fields from two different film frames, so any motion between the frames will appear as a rapid back-and-forth flicker. There can also be noticeable jitter/"stutter" during slow camera pans (telecine judder).

To avoid 3:2 pulldown, film shot specifically for NTSC television is often taken at 30 frame/s.

For viewing native 576i material (such as European television series and some European movies) on NTSC equipment, a standards conversion has to take place. There are basically two ways to accomplish this:

The framerate can be slowed from 25 to 23.976 frames per second (a slowdown of about 4%) to subsequently apply 3:2 pulldown.
Interpolation of the contents of adjacent frames in order to produce new intermediate frames; unless highly sophisticated motion-sensing computer algorithms are applied, this introduces artifacts, and even the most modestly trained of eyes can quickly spot video that has been converted between formats.

Modulation for analog satellite transmission

Because satellite power is severely limited, analog video transmission through satellites differs from terrestrial TV transmission. AM is a linear modulation method, so a given demodulated signal-to-noise ratio (SNR) requires an equally high received RF SNR. The SNR of studio quality video is over 50 dB, so AM would require prohibitively high powers and/or large antennas.

Wideband FM is used instead to trade RF bandwidth for reduced power. Increasing the channel bandwidth from 6 to 36 MHz allows a RF SNR of only 10 dB or less. The wider noise bandwidth reduces this 40 dB power saving by 36 MHz / 6 MHz = 8 dB for a substantial net reduction of 32 dB.

Sound is on a FM subcarrier as in terrestrial transmission, but frequencies above 4.5 MHz are used to reduce aural/visual interference. 6.8, 5.8 and 6.2 MHz are commonly used. Stereo can be multiplex or discrete, and unrelated audio and data signals may be placed on additional subcarrier.

A triangular 60 Hz energy dispersal waveform is added to the composite baseband signal (video plus audio and data subcarrier) before modulation. This limits the satellite downlink power spectral density in case the video signal is lost. Otherwise the satellite might transmit all of its power on a single frequency, interfering with terrestrial microwave links in the same frequency band.

In half transponder mode, the frequency deviation of the composite baseband signal is reduced to 18 MHz to allow another signal in the other half of the 36 MHz transponder. This reduces the FM benefit somewhat, and the recovered SNRs are further reduced because the combined signal power must be "backed off" to avoid intermodulation distortion in the satellite transponder. A single FM signal is constant amplitude, so it can saturate a transponder without distortion.

Field order

An NTSC "frame" consists of an "even" field followed by an "odd" field. As far as the reception of an analog signal is concerned, this is purely a matter of convention and, it makes no difference. It's rather like the broken lines running down the middle of a road, it doesn't matter whether it is a line/space pair or a space/line pair, the effect to a driver is exactly the same.

The introduction of digital television formats has changed things somewhat. Most digital TV formats, including the popular DVD format, record NTSC originated video with the even field first in the recorded frame (the development of DVD took place in regions that traditionally utilize NTSC). However, this frame sequence has migrated through to the so-called PAL format (actually a technically incorrect description) of digital video with the result that the even field is often recorded first in the frame (the European 625 line system is specified as odd frame first). This is no longer a matter of convention because a frame of digital video is a distinct entity on the recorded medium. This means that when reproducing many non NTSC based digital formats (including DVD) it is necessary to reverse the field order otherwise an unacceptable shuddering "comb" effect occurs on moving objects as they are shown ahead in one field and then jump back in the next.

This has also become a hazard where non NTSC progressive video is transcoded to interlaced and vice versa. Systems that recover progressive frames or transcode video should ensure that the "Field Order" is obeyed, otherwise the recovered frame will consist of a field from one frame and a field from an adjacent frame, resulting in "comb" interlacing artifacts. This can often be observed in PC based video playing utilities if an inappropriate choice of de-interlacing algorithm is made.

Comparative quality

Reception problems can degrade an NTSC picture by changing the phase of the color signal (actually differential phase distortion), so the color balance of the picture will be altered unless a compensation is made in the receiver. The vacuum-tube electronics used in televisions through the 1960s led to various technical problems. Among other things, the color burst phase would often drift when channels were changed, which is why NTSC televisions were equipped with a tint control. PAL and SECAM televisions had no need of one, and although it is still found on NTSC TVs, color drifting generally ceased to be a problem once solid-state electronics were adopted in the 1970s. When compared to PAL in particular, NTSC color accuracy and consistency is sometimes considered inferior, leading to video professionals and television engineers jokingly referring to NTSC as Never The Same Color, Never Twice the Same Color, or No True Skin Colors, while for the more expensive PAL system it was necessary to Pay for Additional Luxury. PAL has also been referred to as Peace At Last in the color war. This mostly applied to vacuum tube-based TVs, however, and solid state sets have less of a difference in quality between NTSC and PAL. This color phase, "tint", or "hue" control allows for anyone skilled in the art to easily calibrate a monitor with SMPTE color bars, even with a set that has drifted in its color representation, allowing the proper colors to be displayed. Older PAL television sets did not come with a user accessible "hue" control (it was set at the factory), which contributed to its reputation for reproducible colors.

The use of NTSC coded color in S-Video systems completely eliminates the phase distortions. As a consequence, the use of NTSC color encoding gives the highest resolution picture quality (on the horizontal axis & frame rate) of the three color systems when used with this scheme. (The NTSC resolution on the vertical axis is lower than the European standards, 525 lines against 625) However, it uses too much bandwidth for over-the-air transmission. Some home computers in the 1980s generated S-video, but only for specially designed monitors as no TV at the time supported it. In 1987, a standardized 4-pin DIN plug was introduced for S-video input with the introduction of S-VHS players, which were the first device produced to use the 4-pin plugs. However, S-VHS never became very popular as the picture quality was not significantly better than that of standard VCRs and only high-end TVs supported S-video. Video game consoles in the 1990s began offering S-video output as well, but it was not until high-definition appeared in the 2000s that it became standard on most TVs.
With the advent of DVD players in the 1990s, component video also began appearing. This provides separate lines for the luminance, red shift, and blue shift. Thus, component produces near-RGB quality video. It also allows 480p progressive-scan video due to the greater bandwidth offered. Like S-video, component inputs first appeared on high-end TVs and became standard with high-definition sets.
The mismatch between NTSC's 30 frames per second and film's 24 frames is overcome by a process that capitalizes on the field rate of the interlaced NTSC signal, thus avoiding the film playback speedup used for 576i systems at 25 frames per second (which causes the accompanying audio to increase in pitch slightly, sometimes rectified with the use of a pitch shifter) at the price of some jerkiness in the video. See Framerate conversion above.

Variants

1.SC-M

Unlike PAL, with its many varied underlying broadcast television systems in use throughout the world, NTSC color encoding is invariably used with broadcast system M, giving NTSC-M.

2.SC-J

Only Japan's variant "NTSC-J" is slightly different: in Japan, black level and blanking level of the signal are identical (at 0 IRE), as they are in PAL, while in American NTSC, black level is slightly higher (7.5 IRE) than blanking level. Since the difference is quite small, a slight turn of the brightness knob is all that is required to correctly show the "other" variant of NTSC on any set as it is supposed to be; most watchers might not even notice the difference in the first place. The channel encoding on NTSC-J differs slightly from NTSC-M. In particular, the Japanese VHF band runs from channels 1-12 while the American VHF band uses channels 2-13.

3.AL-M (Brazil)

The Brazilian PAL-M system, introduced in 1972, uses the same lines/field as NTSC (525/60), and almost the same broadcast bandwidth and scan frequency (15.750 vs. 15.734 kHz). Prior to the introduction of color, Brazil broadcast in standard black-and-white NTSC. As a result, PAL-M signals are near identical to North American NTSC signals, except for the encoding of the colour subcarrier (3.575611 MHz for PAL-M and 3.579545 MHz for NTSC). As a consequence of these close specs, PAL-M will display in monochrome with sound on NTSC sets and vice versa.

PAL-M (PAL=Phase Alternating Line) specs are:

Transmission Band UHF/VHF,
Frame Rate 29.97
Lines/Field 525/60
Horizontal Freq. 15.750 kHz
Vertical Freq. 60 Hz
Color Sub Carrier 3.575611 MHz
Video Bandwidth 4.2 MHz
Sound Carrier Frequency 4.5 MHz
Channel Bandwidth 6 MHz

NTSC (National Television System Committee) specs are:

Transmission Band UHF/VHF
Lines/Field 525/60
Horizontal Frequency 15.734 kHz
Vertical Frequency 60 Hz
Color Subcarrier Frequency 3.579545 MHz
Video Bandwidth 4.2 MHz
Sound Carrier Frequency 4.5 MHz

4.AL-N

This is used in Paraguay, Uruguay and Argentina. This is very similar to PAL-M (used in Brazil).

The similarities of NTSC-M and NTSC-N can be seen on the ITU identification scheme table, which is reproduced here:

World television systems
System	Lines	Frame rate	Channel b/w	Visual b/w	Sound offset	Vestigial sideband	Vision mod	Sound mod	Notes
M	525	30	6	4.2	4.5	0.75	Neg.	FM	Most of the Americas and Caribbean, South Korea, Taiwan, Philippines (all NTSC-M) and Brazil (PAL-M).
N	625	25	6	4.2	4.5	0.75	Neg.	FM	Argentina, Paraguay, Uruguay (all PAL-N). Greater number of lines results in higher quality.

As it is shown, aside from the number of lines and frames per second, the systems are identical. NTSC-N/PAL-N are compatible with sources such as game consoles, VHS/Betamax VCRs, and DVD players. However, they are not compatible with broadband broadcasts (which are received over an antenna), though some newer sets come with baseband NTSC 3.58 support (NTSC 3.58 being the frequency for color modulation in NTSC: 3.58 MHz).

5.SC 4.43

In what can be considered an opposite of PAL-60, NTSC 4.43 is a pseudo color system that transmits NTSC encoding (525/29.97) with a color subcarrier of 4.43 MHz instead of 3.58 MHz. The resulting output is only viewable by TVs that support the resulting pseudo-system (usually multi-standard TVs). Using a native NTSC TV to decode the signal yields no color, while using a PAL TV to decode the system yields erratic colors (observed to be lacking red and flickering randomly). The format is apparently limited to few early laserdisc players and some game consoles sold in markets where the PAL system is used.

The NTSC 4.43 system, while not a broadcast format, appears most often as a playback function of PAL cassette format VCRs, beginning with the Sony 3/4" U-Matic format and then following onto Betamax and VHS format machines. As Hollywood has the claim of providing the most cassette software (movies and television series) for VCRs for the world's viewers, and as not all cassette releases were made available in PAL formats, a means of playing NTSC format cassettes was highly desired.

Multi-standard video monitors were already in use in Europe to accommodate broadcast sources in PAL, SECAM, and NTSC video formats. The heterodyne color-under process of U-Matic, Betamax & VHS lent itself to minor modification of VCR players to accommodate NTSC format cassettes. The color-under format of VHS uses a 629 kHz subcarrier while U-Matic & Betamax use a 688 kHz subcarrier to carry an amplitude modulated chroma signal for both NTSC and PAL formats. Since the VCR was ready to play the color portion of the NTSC recording using PAL color mode, the PAL scanner and capstan speeds had to be adjusted from PAL's 50 Hz field rate to NTSC's 59.94 Hz field rate, and faster linear tape speed.

The changes to the PAL VCR are minor thanks to the existing VCR recording formats. The output of the VCR when playing an NTSC cassette in NTSC 4.43 mode is 525 lines/29.97 frames per second with PAL compatible heterodyned color. The multi-standard receiver is already set to support the NTSC H & V frequencies; it just needs to do so while receiving PAL color.

The existence of those multi-standard receivers was probably part of the drive for region coding of DVDs. As the color signals are component on disc for all display formats, almost no changes would be required for PAL DVD players to play NTSC (525/29.97) discs as long as the display was frame-rate compatible.

6. SC-movie

NTSC with a frame rate of 23.976 frame/s is described in the NTSC-movie standard.

Canada/U.S. video game region

Sometimes NTSC-US or NTSC-U/C is used to describe the video gaming region of North America (the U/C refers to U.S. + Canada), as regional lockout usually restricts games released within a region to that region.

Vertical interval reference

The standard NTSC video image contains some lines (lines 1–21 of each field) that are not visible (this is known as the Vertical Blanking Interval, or VBI); all are beyond the edge of the viewable image, but only lines 1–9 are used for the vertical-sync and equalizing pulses. The remaining lines were deliberately blanked in the original NTSC specification to provide time for the electron beam in CRT-based screens to return to the top of the display.

VIR (or Vertical interval reference), widely adopted in the 1980s, attempts to correct some of the color problems with NTSC video by adding studio-inserted reference data for luminance and chrominance levels on line 19.Suitably equipped television sets could then employ these data in order to adjust the display to a closer match of the original studio image. The actual VIR signal contains three sections, the first having 70 percent luminance and the same chrominance as the color burst signal, and the other two having 50 percent and 7.5 percent luminance respectively.

A less-used successor to VIR, GCR, also added ghost (multipath interference) removal capabilities.

The remaining vertical blanking interval lines are typically used for data casting or ancillary data such as video editing timestamps (vertical interval time codes or SMPTE timecodes on lines 12–14), test data on lines 17–18, a network source code on line 20 and closed captioning, XDS, and V-chip data on line 21. Early Teletext applications also used vertical blanking interval lines 14–18 and 20, but Teletext over NTSC was never widely adopted by viewers.

Many stations transmit TV Guide On Screen (TVGOS) data for an electronic program guide on VBI lines. The primary station in a market will broadcast 4 lines of data, and backup stations will broadcast 1 line. In most markets the PBS station is the primary host. TVGOS data can occupy any line from 10-25, but in practice its limited to 11-18, 20 and line 22. Line 22 is only used for 2 broadcast, DirecTV and CFPL-TV.

TiVo data is also transmitted on some commercials and program advertisements so customers can auto record the program being advertised, and is also used in weekly half-hour paid programs on Ion Television and the Discovery Channel which highlight TiVo promotions and advertisers.

What is the NTSC And PAL Setting On DVR?

2011-12-12T23:52:00.000+05:30

Many DVRs are compatible with both NTSC and PAL standards. NTSC standard is predominately in North America and PAL in Europe. The PAL and NTSC standard actually refer to the method used to transmit color. The PAL standard actually requires 2 NTSC decoders to display video (one for each line alternatively) while the NTSC standard only requires one. The NTSC standard is supposedly less accurate in color display, but more efficient in the use of resources. In general, the DVR can be set to either decode NTSC cameras or PAL cameras, but not a combination of both at the same time. If you order a DVR in a package with the security cameras, then you shouldn’t have to worry about the setting or compatibility. If, on the other hand you purchase your cameras from one country, and the DVR from another, then you definitely should make sure that the DVR is compatible with the cameras. Check the standard of the cameras (NTSC or PAL) and the standard of the DVR. Remember that you cannot mix and match the cameras.

Also, keep in mind that just because you are in the USA does not mean you cannot have a PAL DVR or PAL cameras, or because you are in Europe does not mean you cannot have NTSC cameras or DVR. In actuality, you only need to be sure that the cameras and DVR are both compatible.

LCD TV vs. Plasma TV - Which is better ?

2011-12-12T22:53:00.000+05:30

LCD TV vs Plasma TV..

You know you want to buy a flat-screen TV but you don't know if a plasma TV or an LCD TV would be your best choice.

This article explains the differences between plasma versus LCD TVs, and then shows you how to get the best price for a plasma or LCD TV.

LCD TV

LCD (light crystal display) TV screens are made up of a thin layer of liquid crystals sandwiched between two glass plates. When electricity is sent through the crystals an array of tiny multi-colored pixels light up to create a picture.

LCD TV screens are thinner and lighter than plasma screens. They are the most screens for computers, and are quickly gaining popularity as TV screens.

LCD TV screens are anywhere from 1/4" to 4" thick and 2" to 65" wide.

Plasma TV.

A plasma TV screen consists of millions of multi-colored gas-filled cells. When electricity passes through the cells they light up and produce a picture. Plasma TV screens have a much higher resolution than tube TV screens. In fact, the picture is so clear it's almost like watching a scene through a window. Screen sizes range from 42" to 65" wide and are 3" to 4" thick.

Plasma vs. LCD Features

Picture Quality

When it comes to which type of TV screen is sharper and shows more detail, plasma TV have a slight edge over LCD TVs, though LCD TVs are catching up.

Plasma TVs are also slightly better when it comes to viewing angle – how far you can sit to one side of a TV screen before picture quality is affected.

Screen Life

Screen life is the number of hours a TV provides before the picture begins to fade. Plasma TVs have a screen life of about 30,000 to 60,000 hours, depending on the make and model, while LCD TV's have a screen life of 60,000 hours or more.

Plasma TVs are also subject to "burn in". This occurs when a TV displays a still image long enough for a ghost of that image to be burned into the screen. LCD TVs do not have this problem.

HD TV

Both plasma and LCD TVs display HD (high definition) signals for a sharper, more three dimensional picture. LCD TVs, however, have a slightly higher resolution (more screen pixels) then plasma TVs.

Video Games

Plasma and LCD TVs are both great for video gaming, however because of plasma TV's tendency toward screen burn in, an LCD TV is the better choice if you play a lot of video games.

Portability

LCD TVs are thinner and lighter than plasma TVs, making them easier to move and easier to mount on a wall.

Installing Compression Style Connectors to RG59/RG6 cabling

2011-10-23T18:16:00.000+05:30

Installing Compression Style Connectors to RG59/RG6 cabling

1. Connectors are color coded for cable type. See chart below or manufacturer’s recommendation

2. Strip cable to dimensions shown on chart. Remove cable jacket and dielectric
3. Fold exposed braid back over cable jacket leaving smooth foil attached to dielectric
4. For Quad Shield Cable: Fold outer braid back over jacket, remove outer foil and fold inner braid back over jacket.

5. Trim center conductor to proper length, see (A) dimension
6. Insert cable into rear of connector. Insertion depth is shown, on chart. For F-connectors, dielectric should be flush with support mandrel face.

Tips & Tricks:

The key to a good crimp is proper cable & connector preparation
When crimping other mfg’s connectors, minor adjustments to the crimp height may needed. Simply adjust adapter up or down
Keep adapters secured in tool to prevent loss

Tools required: Side cutters, needle nose pliers, X-acto knife, a cable stripper and a BNC crimper.

The stripper is required because the different bands in the coax cable have to be cut precisely to different lengths and depths, and this is difficult to do without the proper tool.

The BNC Crimper is used twice in the process - first to crimp the BNC pin to the main conductor, and then to crimp the collar over the outer insulation at the end of the operation. A quality crimper can make the difference between a connection that works and one that has to be discarded.

It is also a good idea to make a length of test cable and try it out between a couple of computers on the system before actually going through the trouble of pulling cable through wall and ceiling spaces. You don't want to do all that hard work only to find you've got the wrong cabling! The connector itself consists of three parts: the connector itself, the center pin, and the crimp barrel.
STEP 1: PREPARE CABLE
Prepare the end of the cable with the cable stripper tool. Leave yourself a few extra feet of cable length for mistakes. If you get a bad connector, you'll be able to cut it off and try again.
Setting up the cable stripper may require some trial and error adjustment.
Leave about 1/4 inch of cable sticking out the front of the stripper. You then rotate the stripper about the cable until the two layers of insulation and the shielding are cut through to their proper depths.
The center conductor is about 1/2 inch long (it will be cut to fit). The exposed portion of the inner insulation band is about 1/8 inch and the braided shielding between the two insulation bands has been cut back cleanly to the same length as the outer insulation band.
If the cable stripper does not completely do its job, you may have to clean up the cable end with an X-acto knife or needle file. Care counts here. The center conductor should not be nicked, nor should any of the braided shielding be exposed - the most difficult part of this operation is to strip the shielding without damaging the inner insulation band.

STEP 2: CRIMP PIN
Fit the center pin from the connector package over the center conductor as far as it will go. The resulting length of exposed center conductor is the amount of conductor that will have to be cut off for a proper fit. Take the pin back off and cut the center conductor to the correct length with side cutter pliers. It should be 3/16 inch plus or minus. Now when the pin is placed back on the conductor, its base should just reach the inner insulation band (the center conductor should no longer be exposed.)
Place the pin on the center conductor, snug up the crimping tool over the pin (in the special die portion of the crimper provided for the pin) . . . and when you're absolutely sure everything is properly aligned, crimp the pin to the center conductor. Be careful. If this is messed up, you have to start over prepping the cable again with a new connector. Have a few more connectors on hand, even though you'll get good at this, mistakes are made, and if you don't have enough you'll put a real time strain on your project. You will use them!
The base of the pin is seated on the top of the inner insulation band. The crimping process flattens out the pin a bit where the crimping tool applies pressure to it. Clean up any sharp edges left by the crimper with a jeweller’s file, if necessary.

STEP 3: INSTALL BNC CONNECTOR
Slide the Crimp Barrel (or collar) over the cable before installing the connector itself - we will come back to the crimp barrel in the next step, but you have to slide it onto the cable now (you can't force it over the much larger connector later).
You must insert the connector unto the cable. The knurled cylinder portion fits over the pin and inner insulation band and is press-fitted-twisted into place. It has to fit snugly between the outer and inner insulation bands, and during the process, it fights with the braided shielding for this tight space.
When you think you've got the connector inserted under the insulation as far as it will go, push it a little farther. You'll know you're finished when most of the knurled surface has disappeared under the insulation and the center pin is rigid in its seated location inside the connector. If the pin is loose and the connector is on as far as it will go, the length of exposed inner insulation band when the cable was stripped is too short. If the pin is tight but a lot of the knurled portion of the connector is still showing, the length of exposed inner insulation band and/or center conductor when the cable was prepared is too long.

STEP 4: CRIMP BARREL

You're almost done. Now slide the crimp barrel (placed on the cable at the beginning of the last step) up as close to the connector as you can get it.
It will take some effort to get as much of it as possible over the bulge in the cable caused by the last step.
If you have a general-purpose wire stripper/crimper, it has an "ignition terminals" opening that is a little bigger than the cable and a little smaller than the crimp barrel. This is a great tool for putting some leverage behind the crimp barrel when easing it over the bulge in the cable.
Now you can crimp the barrel using the other, larger opening in the BNC crimp tool die. This will tighten and deform the crimp barrel down over the connector and cable for a secure connection.
Crimping the barrel should force the bulge in the cable up over what remains of the exposed knurled portion of the connector to the connector's base. Now you can install another connector on the other end, and then test the completed length of cable. It is good practice to test each length of cable as you go rather than install all the connectors and cabling, and then try to track down a bad connection. With a little practice you will be installing the BNC connectors like a pro.

Installing a Twist-on type BNC Connector

STEP1:

Use a stripping tool to strip the shielding from the coax part of the cable. In order for the connector to go on smoothly you will want about 3/4" of the center conductor showing and about the same amount of the copper wire braid showing (see figure 2 below).

STEP2:

Make sure that none of the strands of copper wire braid touches the middle conductor wire when you twist on the BNC connector. If they accidentally touch, this will not damage the camera but can result in a black (shorted out) image from the camera.

Twist on the BNC Connector onto the wire until it is snug. You will repeat Steps 1 - 3 for the DVR end of the COAX cable.

Installation of the 2 Piece BNC Crimp type connector

A crimp type connection allows for quick and simple installation while still maintaining a mechanical and electrical connection fairly close to a solder type termination. Some of the key points to remember are as follows: Make sure to use the proper size connector for the type of cable you are using. Make sure all cuts and stripping is clean. Avoid nicks as much as possible. Use the proper crimp tool; don't try to improvise with pliers, etc. Follow these steps.

BNC connectors are not hard to install, but they must be installed correctly or they can cause problems down the road. Reproduced below are the instructions from Amphenol (the biggest connector maker). Here is a technique which requires no special tools other than a cable stripper and a crimping tool and which you may find easier than trying to measure the dimensions given in the Amphenol instructions below. You should have a look at the instructions from Amphenol , since some important warnings are contained in them, you may find an easier technique than what is described here.

Place the Plug Body assembly on the work surface
Place the male contact pin on the table with the tip of the pin aligned with the front of the plug assembly
Place the cable next to the pin with the end of the cable just beyond the little hole in the side of the pin
Carefully cut the cable outer sheath right where it lines up with the cable-entry edge of the Plug Body.
Do this with a razor blade or knife being very careful not to nick or cut any of the shield braid wires.
It's better to remove too little sheath than too much. You can remove more later if necessary.
Slide the Outer Ferrule onto the cable
Push back the braid to expose the inner conductor
Using a razor blade or knife, cut off about 4mm (.156 in) of insulation from the end of the inner conductor.
Again, be very careful not to nick any of the conductor wires.

If using RG62 cable (93 ohm) put the little bushing onto the center conductor as shown in the picture below. Bushing not needed for RG58

Place the Male Contact Pin onto the inner conductor, making sure all wires are inside the pin. If the pin doesn't fit snugly against the insulation, remove it and trim the conductors until it does. NO INNER CONDUCTOR WIRES SHOULD BE EXPOSED
Using the appropriate crimp tool (the gold-colored one for RG58, found in the "miscellaneous wrenches" drawer in RM 107) crimp the pin onto the inner conductor
Push the Plug Body Assembly onto the cable until you feel it 'snap' into place. The end of the pin should be flush with the edge of the Plug Body. If you can't push it in far enough because not enough outer sheath was removed in step 4, trim a little more of the outer sheath off until the Plug Body goes all the way on and the pin snaps in. BE VERY CAREFUL AT THIS STEP THAT NO BRAID WIRES ENTER THE PLUG BODY. THIS CAN CAUSE A SHORT.
Push the braid up over the Plug Body and trim it with a cutter or scissors so that it comes just up to the larger diameter part of the Plug Body. It should come all the way up over the knurled or ridged crimp barrel. Having braid wires stick out because they're too long is unsightly, but a greater problem is having them too short and becoming disconnected from the Plug Body.
Slide the Outer Ferrule up over the braid and the plug body as far as it will go, then crimp it in place with the crimp tool.

That's it You're Done!!

IP cameras with Audio Detection

2011-09-11T14:14:00.001+05:30

What is the best IP cameras with audio you used?
What security audio and video applications have you had experience with and what is the best IP cameras with audio you used?
What is IP Camera Audio and Advanced Audio Detection?
-- Many More Question comeout in my mail/phones ...

If you’ve never considered having an audio component with your surveillance system that may be because analog CCTV systms require separate audio and video cables to be installed from end to end which becomes difficult and costly over long distances. IP cameras make the implementation of audio a lot simpler because the audio and video information are sent over the same network cable eliminating the need for extra cabling.

More and more IP camera audio is becoming a common feature not only because it’s easier to process over a network cable but also because the importance of this additional surveillance medium is now being recognized.

Importance of IP Camera Audio:

Detect emergency situations and make sense of other events.
Audio covers a 360° area - surveillance systems coverage is extended beyond the field of view.
Audio detection can trigger email or, other alerts and automatically direct where a camera should record.
Having audio integrated into your surveillance simply gives you more information about a situation. Many times something is brought to our attention first by what we hear, not what we see. Car alarms, gunshots, breaking glass, and screams will not be recognized by a surveillance camera without audio. With 360° coverage, an event happening behind a camera can still be detected.

Three Audio Modes
If you’re considering audio for your appliction your intended use should be clear because it can affect which IP cameras you can select as there are three audio modes available:
Simplex: Audio can be sent in one direction only. Either from the camera only (most likely) or, from the user only.
Half-Duplex: Audio can be sent and received in both directions (to/from camera and user), BUT only in one direction at a time.
Full-Duplex: Audio is sent and received at the same time - similar to a telephone conversation.
For example, Axis offers a camera, the Axis 207MW that offers one-way audio with a built in mic while the Axis M1054 offers two-way audio support with a built-in mic and speaker.
Features such as noise cancellation and echo cancellation are also available that reduce background noise or eliminate feedback.

Audio Detection Alarm
In the same way that an IP camera can analyze video, they can intelligently analyze audio as well. As noted above, audio can hear what the video cannot see. Audio detection complements video motion detection very well because it reacts to events in areas that are too dark for the video motion detector to pick up on.
Audio detection alarms can be programmed so that when any sound (glass breaking, voices in a room, etc.) is detected, they can trigger an IP camera to:
Send & record video and audio
Send email or other alerts
Active external devices - Alarms, floodlights
Trigger a PTZ IP camera to automatically pan to a preset location to begin recording.
Audio detection can be enabled all time, at specific times, or disabled. It can also be configured to trigger an event if a sound level rises above, falls below, or passes a certain level of sound intensity. Sony IP Cameras has a great video demonstration of this function here:
Some of the applicable Sony IP cameras and video servers that have this feature can be found here:
Sony SNC-CH140
Sony SNC-RS46N
Sony SNT-EX101

Audio Compression & Audio Bit Rates:
Audio compression and audio bit rates, just like video compression and video bit rates, are an important consideration when calculating total bandwidth and storage requirements.
Just like video, audio compression uses a codec to reduce the size for efficient transmission and storage. Some audio codecs support CBR (constant bit rate) mode only or both CBR and VBR (variable bit rate) - these factors affect quality and file size.
Bit rate is an important audio setting because it determines the level of compression or, quality of the audio. Generally speaking, the higher the compression level = the lower the bit rate = the lower the audio quality.

Audio/Video Synchronization
Audio and video are two separate packet (data) streams that are sent over a network. For audio and video to play back perfectly syncronized, the two packets must be time-stamped so that they match up.

Best Practices For Audio Implementation
Audio Equipment & Placement: Select a location that will minimize interferring noise and one that’s as close to the source of the sound as possible.
Amplify Audio Signal Early: This minimizes noise in the signal chain.
Acoustical Adjustments: Adjust input gain and use features such as echo cancellation to improve audio quality.
Codec & Bit Rate Selection: Codec and Bit Rate choice affect audio quality. High compression = low quality (but available bandwidth may be a deciding factor).
Shielded Cable: Shielded cable reduces disturbance and noise. Avoid running cable near power cables or high-frequency switching signals.
Legal Implications: What are you allowed to record? Some countries restrict the use of audio and video surveillance - be sure to check with your local authorities.

visit:

NAS, DAS, or SAN? - Choosing the Right Storage Technology ?

2011-08-16T00:00:00.001+05:30

Data is unquestionably the lifeblood of today's digital organization. Storage solutions remain a top priority in IT budgets precisely because the integrity, availability and protection of data are vital to business productivity and success. But the role of information storage far exceeds day to day functions. Enterprises are also operating in an era of increased uncertainty. IT personnel find themselves assessing and planning for more potential risks than ever before, ranging from acts of terrorism to network security threats. A backup and disaster recovery plan is essential, and information storage solutions provide the basis for its execution.

Businesses are also subject to a new wave of regulatory compliance legislation that directly affects the process of storing, managing and archiving data. This is especially true for the financial services and healthcare industries, which handle highly sensitive information and bear extra responsibility for maintaining data integrity and privacy.

Although the need for storage is evident, it is not always clear which solution is right for your organization. There are a variety of options available, the most prevalent being direct-attached storage (DAS), network-attached storage (NAS) and storage area networks (SAN). Choosing the right storage solution can be as personal and individual a decision as buying a home. There is no one right answer for everyone. Instead, it is important to focus on the specific needs and long-term business goals of your organization. Several key criteria to consider include:
• Capacity - the amount and type of data (file level or block level) that needs to be stored and shared
• Performance - I/O and throughput requirements
• Scalability - Long-term data growth
• Availability and Reliability - how mission-critical are your applications?
• Data protection - Backup and recovery requirements
• IT staff and resources available
• Budget concerns
While one type of storage media is usually sufficient for smaller companies, large enterprises will often have a mixed storage environment, implementing different mediums for specific departments, workgroups and remote offices. In this paper, we will provide an overview of DAS, NAS and SAN to help you determine which solution, or combination of solutions, will best help you achieve your business goals.

DAS: Ideal for Local Data Sharing Requirements

Direct-attached storage, or DAS, is the most basic level of storage, in which storage devices are part of the host computer, as with drives, or directly connected to a single server, as with RAID arrays or tape libraries. Network workstations must therefore access the server in order to connect to the storage device. This is in contrast to networked storage such as NAS and SAN, which are connected to workstations and servers over a network. As the first widely popular storage model, DAS products still comprise a large majority of the installed base of storage systems in today's IT infrastructures. Although the implementation of networked storage is growing at a faster rate than that of direct-attached storage, it is still a viable option by virtue of being simple to deploy and having a lower initial cost when compared to networked storage. When considering DAS, it is important to know what your data availability requirements are. In order for clients on the network to access the storage device in the DAS model, they must be able to access the server it is connected to. If the server is down or experiencing problems, it will have a direct impact on users' ability to store and access data. In addition to storing and retrieving files, the server also bears the load of processing applications such as e-mail and databases. Network bottlenecks and slowdowns in data availability may occur as server bandwidth is consumed by applications, especially if there is a lot of data being shared from workstation to workstation.

DAS is ideal for localized file sharing in environments with a single server or a few servers - for example, small businesses or departments and workgroups that do not need to share information over long distances or across an enterprise. Small companies traditionally utilize DAS for file serving and e-mail, while larger enterprises may leverage DAS in a mixed storage environment that likely includes NAS and SAN. DAS also offers ease of management and administration in this scenario, since it can be managed using the network operating system of the attached server. However, management complexity can escalate quickly with the addition of new servers, since storage for each server must be administered separately.

From an economical perspective, the initial investment in direct-attached storage is cheaper. This is a great benefit for IT managers faced with shrinking budgets, who can quickly add storage capacity without the planning, expense, and greater complexity involved with networked storage. DAS can also serve as an interim solution for those planning to migrate to networked storage in the future. For organizations that anticipate rapid data growth, it is important to keep in mind that DAS is limited in its scalability. From both a cost efficiency and administration perspective, networked storage models are much more suited to high scalability requirements.

Organizations that do eventually transition to networked storage can protect their investment in legacy DAS. One option is to place it on the network via bridge devices, which allows current storage resources to be used in a networked infrastructure without incurring the immediate costs of networked storage. Once the transition is made, DAS can still be used locally to store less critical data.
NAS: File-Level Data Sharing Across the Enterprise

Networked storage was developed to address the challenges inherent in a server- based infrastructure such as direct-attached storage. Network-attached storage, or NAS, is a special purpose device, comprised of both hard disks and management software, which is 100% dedicated to serving files over a network. As discussed earlier, a server has the dual functions of file sharing and application serving in the DAS model, potentially causing network slowdowns. NAS relieves the server of storage and file serving responsibilities, and provides a lot more flexibility in data access by virtue of being independent.

NAS is an ideal choice for organizations looking for a simple and cost-effective way to achieve fast data access for multiple clients at the file level. Implementers of NAS benefit from performance and productivity gains. First popularized as an entry-level or midrange solution, NAS still has its largest install base in the small to medium sized business sector. Yet the hallmarks of NAS - simplicity and value - are equally applicable for the enterprise market. Smaller companies find NAS to be a plug and play solution that is easy to install, deploy and manage, with or without IT staff at hand. Thanks to advances in disk drive technology, they also benefit from a lower cost of entry.

In recent years, NAS has developed more sophisticated functionality, leading to its growing adoption in enterprise departments and workgroups. It is not uncommon for NAS to go head to head with storage area networks in the purchasing decision, or become part of a NAS/SAN convergence scheme. High reliability features such as RAID and hot swappable drives and components are standard even in lower end NAS systems, while midrange offerings provide enterprise data protection features such as replication and mirroring for business continuance. NAS also makes sense for enterprises looking to consolidate their direct-attached storage resources for better utilization. Since resources cannot be shared beyond a single server in DAS, systems may be using as little as half of their full capacity. With NAS, the utilization rate is high since storage is shared across multiple servers.

The perception of value in enterprise IT infrastructures has also shifted over the years. A business and ROI case must be made to justify technology investments. Considering the downsizing of IT budgets in recent years, this is no easy task. NAS is an attractive investment that provides tremendous value, considering that the main alternatives are adding new servers, which is an expensive proposition, or expanding the capacity of existing servers, a long and arduous process that is usually more trouble than it's worth. NAS systems can provide many terabytes of storage in high density form factors, making efficient use of data center space. As the volume of digital information continues to grow, organizations with high scalability requirements will find it much more cost-effective to expand upon NAS than DAS. Multiple NAS systems can also be centrally managed, conserving time and resources.

Another important consideration for a medium sized business or large enterprise is heterogeneous data sharing. With DAS, each server is running its own operating platform, so there is no common storage in an environment that may include a mix of Windows, Mac and Linux workstations. NAS systems can integrate into any environment and serve files across all operating platforms. On the network, a NAS system appears like a native file server to each of its different clients. That means that files are saved on the NAS system, as well as retrieved from the NAS system, in their native file formats. NAS is also based on industry standard network protocols such as TCP/IP, FC and CIFS.

SANs: High Availability for Block-Level Data Transfer

A storage area network, or SAN, is a dedicated, high performance storage network that transfers data between servers and storage devices, separate from the local area network. With their high degree of sophistication, management complexity and cost, SANs are traditionally implemented for mission-critical applications in the enterprise space. In a SAN infrastructure, storage devices such as NAS, DAS, RAID arrays or tape libraries are connected to servers using Fibre Channel. Fibre Channel is a highly reliable, gigabit interconnect technology that enables simultaneous communication among workstations, mainframes, servers, data storage systems and other peripherals. Without the distance and bandwidth limitations of SCSI, Fibre Channel is ideal for moving large volumes of data across long distances quickly and reliably.

In contrast to DAS or NAS, which is optimized for data sharing at the file level, the strength of SANs lies in its ability to move large blocks of data. This is especially important for bandwidth-intensive applications such as database, imaging and transaction processing. The distributed architecture of a SAN also enables it to offer higher levels of performance and availability than any other storage medium today. By dynamically balancing loads across the network, SANs provide fast data transfer while reducing I/O latency and server workload. The benefit is that large numbers of users can simultaneously access data without creating bottlenecks on the local area network and servers.

SANs are the best way to ensure predictable performance and 24x7 data availability and reliability. The importance of this is obvious for companies that conduct business on the web and require high volume transaction processing. Another example would be contractors that are bound to service-level agreements (SLAs) and must maintain certain performance levels when delivering IT services. SANs have built in a wide variety of failover and fault tolerance features to ensure maximum uptime. They also offer excellent scalability for large enterprises that anticipate significant growth in information storage requirements. And unlike direct-attached storage, excess capacity in SANs can be pooled, resulting in a very high utilization of resources. There has been much debate in recent times about choosing SAN or NAS in the purchasing decision, but the truth is that the two technologies can prove quite complementary. Today, SANs are increasingly implemented in conjunction with NAS. With SAN/NAS convergence, companies can consolidate block-level and file-level data on common arrays.

Even with all the benefits of SANs, several factors have slowed their adoption, including cost, management complexity and a lack of standardization. The backbone of a SAN is management software. A large investment is required to design, develop and deploy a SAN, which has limited its market to the enterprise space. A majority of the costs can be attributed to software, considering the complexity that is required to manage such a wide scope of devices. Additionally, a lack of standardization has resulted in interoperability concerns, where products from different hardware and software vendors may not work together as needed. Potential SAN customers are rightfully concerned about investment protection and many may choose to wait until standards become defined.

Conclusion

With such a variety of information storage technologies available, what is the best way to determine which one is right for your organization? DAS, NAS and SAN all offer tremendous benefits, but each is best suited for a particular environment. Consider the nature of your data and applications. How critical and processing-intensive are they? What are your minimum acceptable levels of performance and availability? Is your information sharing environment localized, or must data be distributed across the enterprise? IT professionals must make a comprehensive assessment of current requirements while also keeping long-term business goals in mind.

Like all industries, storage networking is in a constant state of change. It's easy to fall into the trap of choosing the emerging or disruptive storage technology at the time. But the best chance for success comes with choosing a solution that is cost-correct and provides long term investment protection for your organization. Digital assets will only continue to grow in the future. Make sure your storage infrastructure is conducive to cost-effective expansion and scalability. It is also important to implement technologies that are based on open industry standards, which will minimize interoperability concerns as you expand your network.

Which Image Quality is Better

2011-08-14T20:54:00.000+05:30

When thinking about maximizing image quality, resolution is usually the first thing that comes to mind. However, resolution is not the only factor that impacts quality. The amount of bandwidth available and used can have a dramatic impact on image quality. In this report, we examine bandwidth and the effect that it has on quality across numerous cameras.
Which Image Quality is Better?
To better understand image quality, let's start by examining two samples of the same scene side by side:

Consider two questions:

1. Which camera has higher resolution? A or B?

2. Which camera is better? A or B?

It is pretty obvious that the image from Camera B is better so this should be a simple case.

The reality is that those images are from the same camera at the same resolution and frame rate (720p/30). All that was done to the camera was changing the Constant Bit Rate target from 512 Kb/s to 8 Mb/s.

Factors Impacting Quality:

Even with the same resolution, two common settings impact quality:

1. Bit Rate: Most cameras can have their bit rate adjusted to specific levels (e.g., 512 Kb/s, 2 Mb/s, 8Mb/s, etc.)

2. Quantization Level: Most cameras can have the level of compression adjusted (often called a quality or compression setting with options from 1-10 or 0-100)

Typically, these are mutually exclusive. If you lock in bit rate, the camera will automatically adjust the quantization level to not exceed the bandwidth set. Vice versa, if you set the quantization level, the camera will automatically change the bandwidth consumed to make sure the quality / compression always stays at the same level.

Our Test Process

We wanted to better understand how changes in these two factors impact video quality. To do so, we did a series of tests with three HD cameras: the Axis P1344, the Sony CH140 and the Bosch NBN-921.

For the bandwidth tests, we tested each camera at the following levels:

512 Kb/s
1 Mb/s
2 Mb/s
4 Mb/s
8 Mb/s

We did this across a series of scenes to see how quality would vary in different conditions:

Daytime Indoors (300 lux)
Nighttime Indoors (.5 lux)
Daytime Intersection

Finally, we did a similar series of tests varying the quality level of a VBR camera (the Axis across 0, 30, 60 and 100 levels) to better understand changes in quality and bandwidth consumption.

RAW Formats

2011-08-14T20:02:00.001+05:30

RAW Format implies that there is no compression done on the image. The major types of RAW format are RGB, YUV, YIQ. Our eye is more sensitive towards light intensity variation than color variation. So loss on color information will not affect the over all quality of the image. RGB is an end stream format. Information from the image sensor is in RGB format and we need the same format for displaying the image on an end
device. YUV & YIQ formats are developed for Analog TV transmission (NTSC & PAL respectively) and the digital version of YUV, YCbCr is the most common format used for image and video compressions.
Conversion from one format to another is described below:
RGB to YCbCr Conversion
Y = 0.299 R + 0.587 G + 0.11B
Cb = 0.564 (B - Y)
Cr = 0.713 (R - Y)
YCbCr to RGB
R = Y + 1.402 Cr
G = Y – 0.344 Cb – 0.714 C r
B = Y + 1.722 Cb
Y – Luminance Signal
Cb, Cr – Chrominance Signal, Color difference signal
R – Red
G – Green
B – Blue
Need for Compression
Consider an image of resolution 640 × 480. Let us calculate the size of the picture in RAW format. Each of the 10 Color is represented by 8 bits. Then for each pixel it needs 24 bits. Total no of pixels in the image is 640 × 480 = 307200 pixels. Therefore the size of the image turns to 307200 × 3 bytes = 921600 bytes. But an image in compressed format with the same resolution takes only 100 KB.
In the case of RAW video stream of length 1 sec its needs 640 × 480 × 3 × 25 = 23040000 bytes (23 MB) of storage if the frame rate is 25 frames/sec. But it’s known that the VCD format video having a size 700 MB plays for around 80 minutes. In the former case we need 110400 MBs (23 MB × 60 × 80) as storage space for 80 minutes video. Therefore we can achieve a high compression 150: 1 at the cost of computational complexities.

IP CCTV transmission methods

2011-08-14T18:33:00.000+05:30

There are essentially three ways of transmitting video streams over the network from the source to the destination: broadcast, unicast and multicast.

Broadcast
Broadcast is defined as a one-to-all communication between the source and the destinations. In IP video surveillance, the source refers usually to the IP camera and the destination refers to the monitoring station or the recording server. In this case, broadcasting would mean that the IP camera would send the video stream to all monitoring stations and recording servers, but also to any IP devices on the network, even though only a few specific destination sources had actually requested the stream. Typically, this method of transmission is not commonly used in IP video surveillance applications, but can be seen more often in the TV broadcasting industry where TV signals are switched at the destination level.

Unicast
Unicast is defined as a one-to-one communication between the source and the destination. Unicast transmissions are usually done in TCP or UDP and require a direct connection between the source and the destination. In this scenario, the IP camera (source) needs to have the capabilities to accept many concurrent connections when many destinations want to view or record that same video at the same time.
In terms of video streaming in unicast transmission, the IP camera will stream as many copies of the video feed requested by the destinations. In figure 1 below, three copies of the same video stream are sent over the network; one copy for each of the three destinations requesting the stream. If each video stream is 4 Mbps, this transmission will produce 12 Mbps (3x4Mbps) of data on multiple network segments.

As a result, many destinations connected in unicast to a video source can result in high network traffic. In other words, if we imagine a large system with 200 destinations requesting the same video stream, we would end up having 800 Mbps (200x4Mbps) of data travelling over the network, which is realistically unmanageable. Although this method of transmission is widely used over the Internet where most routers are not multicast-enabled, within a corporate LAN, unicast transmission is not necessarily the best practice as it can quickly increase the bandwidth needed for viewing and recording camera streams.

Multicast
In multicast transmission, there is no direct connection between the source and the destinations. The connection to the video stream of the IP camera is done by joining a multicast group, which in simple terms means actually connecting to the multicast IP address of the video stream. So the IP camera only sends a single copy of the video stream to its designated IP address and the destination simply connects to the stream available over the network with no additional overhead on the source. In other words, the destinations share the same video stream. In figure 2 below, the same three destinations requesting the video stream have the same impact on the network as a single destination requesting the stream in unicast and there is no more than 4 Mbps of data travelling on each segment of the network. Even with 200 destinations requesting that video stream, the same amount of data would be travelling on the network.

It is evident at this point that using multicast transmissions in an IP video surveillance application can save a lot of bandwidth, especially in large scale deployments where the number of destinations can grow very quickly.

Bandwidth optimisation for IP CCTV
When it comes to IP video surveillance, it is important to efficiently manage the way video streams are transmitted over the network in order not to overload the available bandwidth. Even though IT infrastructures are built to handle any kind of data, the applications generating traffic over the IP network need to be conducive with the efficient utilization of the network resources in place. To this end, different functionalities and mechanisms are offered by IP video surveillance solution providers to allow optimization of bandwidth and network resources such as:
• Multicasting
• Multistreaming
• Video compression

Even though the capacity and speed of the network are constantly increasing and its associated costs are declining, this is still not a good reason for users to ignore the additional investments and efforts needed to optimise bandwidth management. The amount of data travelling on the network is also still on the rise and therefore, investments in bandwidth optimization are ones that can contribute to a reduction in total cost of ownership, specifically in respect to efficiency gains and maximized resources.

For example, in video surveillance, more and more end-users are requesting cameras with higher picture quality and resolution, often opting for high-definition and megapixel cameras. These types of cameras require much more bandwidth than standard definition cameras. Also, more and more people inside as well as outside an organization’s walls are requesting access to video streams over the network. In the case where a large number of users are simultaneously trying to access a specific video stream, efficient use of network resources can be crucial in avoiding overloaded capacity and entire network crashes.
It is equally important to realize that optimizing the bandwidth on the network does not necessarily go hand in hand with large capital investments, but is more a matter of putting the right solutions in place and leveraging the unique and powerful capabilities of these solutions.

How to Selecting the right CCTV video compression

2011-08-14T15:30:00.003+05:30

If you are responsible for planning or designing a new CCTV video surveillance system, you have to make a technology choice regarding which video compression technique to use.

For sure, it will be digital. But which video compression scheme is the most suitable for your application?

1. Motion JPEG CCTV video compression
The JPEG standard was developed by the Joint Photographic Expert Group (part of ISO) for efficient storage of individual frames. Motion JPEG or M-JPEG is a series of separate JPEG images that form a video sequence. When 16 JPEG image frames or more are joined together per second, the result is an illusion of motion video. Video reproduction at 30 frames per second (FPS) for NTSC signals or 25 FPS for PAL signals is called full motion video or continuous-motion video.

Although Motion JPEG is an unlicensed standard it is widely compatible with many applications that require low frame rates or technologies such as Video Analytics where frame by frame analysis is crucial.

Advantages
1. Ability to support multi-mega pixel resolution.
2. Ideal for courtroom single frame evidence.
3. Clearer images at lower frame rates than MPEG-4.
4. Frame by frame playback offers more frames to view.
5. Technology is simpler; this can reduce the cost of a camera or video codec.
6. At low bandwidth priority is given to Image Resolution.
Disadvantages
1. High bit rate for scenes with little or no activity increases bandwidth and storage.
2. Video quality deteriorates at higher compression ratios.
3. No M-JPEG standard often means incompatibility issues.
4. Converting M-JPEG into another format reduces video quality.
5. Dated technology superseded by more bandwidth-efficient encoding techniques.

MPEG-4 CCTV video compression
MPEG-4 is a compression standard that was introduced in late 1998 by the Moving Picture Experts Group. In video surveillance applications MPEG-4 Part 2, also known as MPEG-4 Visual is the version of MPEG-4 most commonly used. MPEG-4 supports both low-bandwidth applications and those applications that require high quality images, with virtually unlimited bandwidth and no limitations in frame-rate. Typically most MPEG-4 based encoders and cameras support video up to DVD quality.

MPEG-4 is much more efficient than M-JPEG because video frames are analysed prior to being sent across the network. The first compressed image (I frame) is used as a reference point, the following images only contain information that differs to the initial I frame reference image. Periodically I frames are transmitted within the video sequence to ensure a recent reference point. The distance between these I frames is known as the GOP (Group of Pictures). The distance between I frames is usually user definable depending on the application and activity in the scene. For example a 25 FPS video stream with a GOP of 50 would mean a new I frame with GOP change information is sent every 2 seconds. The viewing application on the receiving end of the transmission then reconstructs all images based on this information and displays the video.

Advantages
1. MPEG-4 up to 5 times more efficient than M-JPEG at low bandwidths.
2. Increases the amount of time video can be stored compared with M-JPEG.
3. Uses less network bandwidth when compared with M-JPEG.
4. Very efficient at high frame rates.
Disadvantages
1. When the bit-rate is limited video quality suffers.
2. Low efficiency at very low frame-rates or extremely high scene activity.
3. Can be liable to “blurring” on freeze frame or very high motion.

H.264 CCTV video compression
H.264 is the latest MPEG standard for video encoding that is geared to take video beyond the realms of DVD quality by supporting Hi Definition CCTV video. H.264 can also reduce the size of digital video by more than 80% compared with M-JPEG and as much as 50% with MPEG-4, all without compromising image quality. This means that much less network bandwidth and storage space are required. Since the typical storage costs for surveillance projects represent between 20 and 30 percent of the project cost significant savings can be made.

Like many sectors of our industry, the devil is in the detail and system integrators and end-users who wish to see the benefits of an IP-based solution should look to someone who really knows the technology and can give an impartial view. It is common sense that manufacturers will only support their own hardware and will promise the earth for it, whereas a distributor will have evaluated a number of solutions from different vendors and be able to say that product A is the best for solution B because of XYZ whereas product Y is the best for solution C because of etc etc.

Advantage
1. H.264 cameras is that they reduce the amount of bandwidth needed.if your megapixel camera needed 10 Mb/s before (with MJPEG), it might now need only 1.5 Mb/s. So for each camera, you will save a lot of bandwidth.
2. Eliminates barriers: Enables many more networks to support megapixel cameras.
3. The bitstream is fully compatible with existing decoders with no error/drift.
Disadvantages
1. Using analytics with these cameras reduces the H.264 benefit.
2. Costs few hundred dollars more per camera.

TCP VS UDP & IP Topics

2011-04-30T00:54:00.000+05:30

Can you explain the difference between UDP and TCP internet protocol (IP) traffic and its usage with an example?
A. Transmission Control Protocol (TCP) and User Datagram Protocol (UDP)is a transportation protocol that is one of the core protocols of the Internet protocol suite. Both TCP and UDP work at transport layer TCP/IP model and both have very different usage.

Difference between TCP and UDP

TCP	UDP
Reliability: TCP is connection-oriented protocol. When a file or message send it will get delivered unless connections fails. If connection lost, the server will request the lost part. There is no corruption while transferring a message.	Reliability: UDP is connectionless protocol. When you a send a data or message, you don't know if it'll get there, it could get lost on the way. There may be corruption while transferring a message.
Ordered: If you send two messages along a connection, one after the other, you know the first message will get there first. You don't have to worry about data arriving in the wrong order.	Ordered: If you send two messages out, you don't know what order they'll arrive in i.e. no ordered
Heavyweight: - when the low level parts of the TCP "stream" arrive in the wrong order, resend requests have to be sent, and all the out of sequence parts have to be put back together, so requires a bit of work to piece together.	Lightweight: No ordering of messages, no tracking connections, etc. It's just fire and forget! This means it's a lot quicker, and the network card / OS have to do very little work to translate the data back from the packets.
Streaming: Data is read as a "stream," with nothing distinguishing where one packet ends and another begins. There may be multiple packets per read call.	Datagrams: Packets are sent individually and are guaranteed to be whole if they arrive. One packet per one read call.
Examples: World Wide Web (Apache TCP port 80), e-mail (SMTP TCP port 25 Postfix MTA), File Transfer Protocol (FTP port 21) and Secure Shell (OpenSSH port 22) etc.	Examples: Domain Name System (DNS UDP port 53), streaming media applications such as IPTV or movies, Voice over IP (VoIP), Trivial File Transfer Protocol (TFTP) and online multiplayer games etc

Security Camera Selection Guide

2011-02-27T01:04:00.006+05:30

ON Sunday, November 8, 2009 we discuss a Guide for choosing the CCTV system, now we know how to select a Security camera.( http://arindamcctvaccesscontrol.blogspot.com/2009/11/guide-for-choosing-cctv-system.html )

Security cameras are literally the eyes of a video surveillance system. Cameras should be deployed in critical areas to capture relevant video.
The two basic principles of camera deployment are (1) use chokepoints and (2) cover assets.
Chokepoints are areas where people or vehicles must pass to enter a certain area. Examples include doorways, hallways and driveways. Placing cameras at chokepoints is a very cost-effective way to document who entered a facility.
Assets are the specific objects or areas that need security. Examples of assets include physical objects such as safes and merchandise areas as well as areas where important activity occurs such as cash registers, parking spots or lobbies. What is defined as an asset is relative to the needs and priorities of your organization.

1. Security Camera Selection

Once you determine what areas you want to cover, there are four camera characteristics to decide on:
1. Fixed vs. PTZ: A camera can be fixed to only look at one specific view or it can be movable through the use of panning, tilting and zooming (i.e., moving left and right, up and down, closer and farer away). Most cameras used in surveillance are fixed. PTZ cameras are generally used to cover wider fields of views and should generally be used only if you expect a monitor to actively use the cameras on a daily basis. A key reason fixed cameras are generally used is that they cost 5 to 8 times less than PTZs (fixed cameras average $200 to $500 USD whereas PTZ cameras can be over $2,000 USD).

2. Color vs. Infrared vs. Thermal: In TV, a video can be color or black and white. In video surveillance today, the only time producing a black and white image makes sense is when lighting is very low (e.g., night time). In those conditions, infrared or thermal cameras produce black and white images. Infrared cameras require special lamps (infrared illuminators) that produce clear image in the dark (but are significantly more expensive than color cameras - often 2x to 3x more). Thermal cameras require no lighting but product only silhouettes of objects and are very expensive ($5,000 to $20,000 on average) In day time or lighted areas, color cameras are the obvious choice as the premium for color over black and white is trivial.

3. Standard Definition vs. Megapixel: This choice is similar to that of TVs. Just like in the consumer world, historically everyone used standard definition cameras but now users are shifting into high definition cameras. While high definition TV maxes out at 3 MP, surveillance cameras can provide up to 16 MP resolutions. In 2008, megapixel cameras only represent about 4% of total cameras sold but they are expanding very rapidly.
4. IP vs. Analog: The largest trend in video surveillance today is the move from analog cameras to IP cameras. While all surveillance cameras are digitized to view and record on computers, only IP cameras digitize the video inside the camera. While most infrared and thermal cameras are still only available as analog cameras, you can only use megapixel resolution in IP cameras. Currently, 20% of cameras sold are IP and this percentage is increasingly rapidly.

Most organizations will mix and match a number of different camera types. For instance, an organization may use infrared fixed analog cameras around a perimeter with an analog PTZ overlooking the parking lot. On the inside, they may have a fixed megapixel camera covering the warehouse and a number of fixed IP cameras covering the entrance and hallways.

2. Connectivity

In professional video surveillance, cameras are almost always connected to video management systems for the purpose of recording and managing access to video. There are two main characteristics to decide on for connectivity.
• IP vs. Analog: Video can be transmitted over your computer network (IP) or it can be sent as native analog video. Today, most video feeds are sent using analog but migration to IP transmission is rapidly occurring. Both IP cameras and analog cameras can be transmitted over IP. IP cameras can connect directly to an IP network (just like your PC). Analog cameras cannot directly connect to an IP network. However, you can install an encoder to transmit analog feeds over IP. The encoder has an input for an analog camera video feed and outputs a digital stream for transmission over an IP network.
• Wired vs. Wireless: Video can be sent over cables or though the air, whether you are using IP or analog video. Over 90% of video is sent over cables as this is generally the cheapest and most reliable way of sending video. However, wireless is an important option for transmitting video as deploying wires can be cost-prohibitive for certain applications such as parking lots, fence lines and remote buildings.

3. Video Management System

Video management systems are the hub of video surveillance solutions, accepting video from cameras, storing the video and managing distribution of video to viewers.
There are four fundamental options in video management systems. Most organizations choose one of the four. However, it's possible that companies may have multiple types when they transition between one to another.
• DVRs are purpose built computers that combine software, hardware and video storage all in one. By definition, they only accept analog camera feeds. Almost all DVRs today support remote viewing over the Internet. DVRs are very simple to install but they significantly limit your flexibility in expansion and hardware changes. DVRs are still today the most common option amongst professional buyers. However, DVRs have definitely fallen out of favor and the trend is to move to one of the three categories below.

• HDVRs or hybrid DVRs are DVRs that support IP cameras. They have all the functionality of a DVR listed above plus they add support for IP and megapixel cameras. Most DVRs can be software upgraded to become HDVRs. Such upgrades are certainly a significant trend and is attractive because of the low migration cost (supports analog and IP cameras directly).
• NVRs are like DVRs in all ways except for camera support. Whereas a DVR only supports analog cameras, an NVR only supports IP cameras. To support analog cameras with an NVR, an encoder must be used.

• IP Video Surveillance Software is a software application, like Word or Excel. Unlike DVRs or NVRs, IP video surveillance software does not come with any hardware or storage. The user must load and set up the PC/Server for the software. This provides much greater freedom and potentially lower cost than using DVR/NVR appliances. However, it comes with significant more complexity and time to set up and optimize the system. IP video surveillance software is the hottest trend in video management systems currently and is the most frequent choice for very large camera counts (hundreds or more).

4. Storage

Surveillance video is almost always stored for later retrieval and review. The average storage duration is between 30 and 90 days. However, a small percentage of organization store video for much shorter (7 days) or for much longer (some for a few years).
The two most important drivers for determining storage duration is the cost of storage and the security threats an organization faces.
While storage is always getting cheaper, video surveillance demands huge amount of storage. For comparison, Google's email service offer about 7 GB/s of free email storage. This is considered to be an enormous amount for email. However, a single camera could consume that much storage in a day. It is fairly common for video surveillance systems to require multiple TBs of storage even with only a few dozen cameras. Because storage is such a significant cost, numerous techniques exist to optimize the use of storage.
The type of security threats also impact determining storage duration. For instance, a major threat at banks is the report of fraudulent investigations. These incidents are often not reported by affected customers until 60 or 90 days after the incident. As such, banks have great need for longer term storage. By contrast, casinos usually know about issues right away and if a problem is to arise they learn about it in the same week. Casinos then, very frequently, use much shorter storage duration (a few weeks is common).
Three fundamental types of storage may be selected:
• Internal storage uses hard drives built inside of a DVR, NVR or server. Today this is still the most common form of storage. With hard drives of up to 1 TB common today, internal storage can provide total storage of 2TB to 4TB. Internal storage is the cheapest option but tends to be less reliable and scalable than the other options. Nonetheless, it is used the most frequently in video surveillance.

• Directly Attached storage is when hard drives are located outside of the DVR, NVR or server. Storage appliances such as NAS or SANs are used to manage hard drives. This usually provides greater scalability, flexibility and redundancy. However, the cost per TB is usually more than internal storage. Attached storage is most often used in large camera count applications.

• Storage Clusters are IP based 'pools' of storage specialized in storing video from large numbers of cameras. Multiple DVRs, NVRs or servers can stream video to these storage clusters. They provide efficient, flexible and scalable storage for very large camera counts. Storage clusters are the most important emerging trend in video surveillance storage.

5. Video Analytics

Video analytics scan incoming video feeds to (1) optimize storage or (2) to identify threatening/interesting events.
Storage optimization is the most commonly used application of video analytics. In its simplest form, video analytics examines video feeds to identify changes in motion. Based on the presence or absence of motion, the video management system can decide not to store video or store video at a lower frame rate or resolution. Because surveillance video captures long periods of inactivity (like hallways and staircases, buildings when they are closed, etc.), using motion analytics can reduce storage consumption by 60% - 80% relative to continuously recording.
Using video analytics to identify threatening/interesting events is the more 'exciting' form of video analytics. Indeed, generally when industry people talk of video analytics, this is their intended reference. Common examples of this are perimeter violation, abandoned object, people counting and license plate recognition. The goal of these types of video analytics is to pro-actively identify security incidents and to stop them in progress (e.g., perimeter violation spots a thief jumping your fence so that you can stop them in real time, license plate recognition identifies a vehicle belonging to a wanted criminal so you can apprehend him).
These video analytics have been generally viewed as a disappointment. While many observers believe that video analytics will improve, the video analytics market is currently contracting (in response to its issues and the recession).

6. Viewing Video

Surveillance video is ultimately viewed by human beings. Most surveillance video is never viewed. Of the video that is viewed, the most common use is for historical investigations. Some surveillance video is viewed live continuously, generally in retail (to spot shoplifters) and in public surveillance (to identify criminal threats. Most live video surveillance is done periodically in response to a 'called-in' threat or to check up on the status of a remote facility.
Four fundamental options exist for viewing video:
• Local Viewing directly from the DVR, NVR or servers is ideal for monitoring small facilities on site. This lets the video management system double as a viewing station, saving you the cost of setting up or using a PC. This approach is most common in retailers, banks and small businesses.

• Remote PC Viewing is the most common way of viewing surveillance video. In this approach, standard PCs are used to view live and recorded video. Either a proprietary application is installed on the PC or a web browser is used. Most remote PC viewing is done with an installed application as it provides the greatest functionality. However, as web applications mature, more providers are offering powerful web viewing. The advantage of watching surveillance video using a web browser is that you do not have to install nor worry about upgrading a client.

• Mobile Viewing allows security operators in the field to immediately check surveillance video. As responders and roving guards are common in security, mobile viewing has great potential. Though mobile clients have been available for at least 5 years, they have never become mainstream due to implementation challenges with PDAs/phones. Renewed interest and optimism has emerged with the introduction of the Apple iPhone.
• Video Wall Viewing is ideal for large security operation centers that have hundreds or thousands of cameras under their jurisdiction. Video walls provide very large screens so that a group of people can simultaneously watch. This is especially critical when dealing with emergencies. Video walls generally have abilities to switch between feeds and to automatically display feeds from locations where alarms have been triggered.

7. Integrating Video with Other Systems

Many organizations use surveillance video by itself, simply pulling up the video management systems' client application to watch applications. However, for larger organizations and those with more significant security concerns, this is an inefficient and poor manner to perform security operations. Instead, these organizations prefer an approach similar to the military's common operational picture (COP) where numerous security systems all display on a singular interface.
Three ways exist to deliver such integration with video surveillance:
• Access Control as Hub: Most organizations have electronic/IP access control systems. These systems have been designed for many years to integrate with other security systems such as intrusion detection and video surveillance. This is the most way to integrate video surveillance and relatively inexpensive ($10,000 - $50,000 USD). However, access control systems are often limited in the number and depth of integration they support.

• PSIM as Hub: In the last few years, manufacturers now provide specialized applications whose sole purpose are to aggregate information from security systems (like video surveillance) and provide the most relevant information and optimal response policies. These applications tend to be far more expensive (($100,000 - $1,000,000 USD) yet support a far wider range of security manufacturers and offer more sophisticated features.

• Video Management System as Hub: Increasingly, video management systems are adding in support for other security systems and security management features. If you only need limited integration, your existing video management system may provide an inexpensive (yet limited) solution.

8.Video Resolutions

1.Analog Video Resolutions
Video surveillance solutions use a set of standard resolutions. National Television System Committee (NTSC) and Phase Alternating Line (PAL) are the two prevalent analog video standards. PAL is used mostly in Europe, China, and Australia and specifies 625 lines per-frame with a 50-Hz refresh rate. NTSC is used mostly in the United States, Canada, and portions of South America and specifies 525 lines per-frame with a 59.94-Hz refresh rate.
These video standards are displayed in interlaced mode, which means that only half of the lines are refreshed in each cycle. Therefore, the refresh rate of PAL translates into 25 complete frames per second and NTSC translates into 30 (29.97) frames per second..

Table of Analog Video Resolutions (in pixels)
Format	NTSC-Based (in pixels)	PAL-Based (in pixels)
QCIF	176 × 120	176 × 144
CIF	352 × 240	352 × 288
2CIF	704 x 240	704 x 288
4CIF	704 × 480	704 × 576
D1	720 × 480	720 × 576

Note that the linear dimensions of 4CIF are twice as big as CIF. As a result, the screen area for 4CIF is four times that of CIF with higher bandwidth and storage requirements. The 4CIF and D1 resolutions are almost identical and sometimes the terms are used interchangeably.

2.Digital Video Resolutions
User expectations for resolution of video surveillance feeds are increasing partially due to the introduction and adoption of high-definition television (HDTV) for broadcast television. A 4CIF resolution, which is commonly deployed in video surveillance, is a 4/10th megapixel resolution. The HDTV formats are megapixel or higher. Table lists the typical resolutions available in the industry.

Size/ Format	Pixels
QQVGA	160x120
QVGA	320x240
VGA	640x480
HDTV	1280x720
1M	1280x960
1M	1280x1024
2M	1600x1200
HDTV	1920x1080
3M	2048x1536

While image quality is influenced by the resolution configured on the camera, the quality of the lens, sharpness of focus, and lighting conditions also come into play. For example, harshly lighted areas may not offer a well-defined image, even if the resolution is very high. Bright areas may be washed out and shadows may offer little detail. Cameras that offer wide dynamic range processing, an algorithm that samples the image several times with differing exposure settings and provides more detail to the very bright and dark areas, can offer a more detailed image.

As a best practice, do not assume the camera resolution is everything in regards to image quality. For a camera to operate in a day-night environment, (the absence of light is zero lux), the night mode must be sensitive to the infrared spectrum. It is highly recommended to conduct tests or pilot installations before buying large quantities of any model of camera.

How a Smart Card Reader Works

2011-01-23T18:08:00.002+05:30

Smart Card Readers are also known as card programmers (because they can write to a card), card terminals, card acceptance device (CAD) or an interface device (IFD). There is a slight difference between the card reader and the terminal. The term 'reader' is generally used to describe a unit that interfaces with a PC for the majority of its processing requirements. In contrast, a 'terminal' is a self-contained processing device.
Smart cards are portable data cards that must communicate with another device to gain access to a display device or a network. Cards can be plugged into a reader, commonly referred to as a card terminal, or they can operate using radio frequencies (RF).
When the smart card and the card reader come into contact, each identifies itself to the other by sending and receiving information. If the messages exchanged do not match, no further processing takes place. So, unlike ordinary bank cards, smart cards can defend themselves against unauthorized users and uses in innovative security measures.

Communicating with a Smart Card Reader
The reader provides a path for your application to send and receive commands from the card. There are many types of readers available, such as serial, PCCard, and standard keyboard models. Unfortunately, the ISO group was unable to provide a standard for communicating with the readers so there is no one-size-fits-all approach to smart card communication.
Each manufacturer provides a different protocol for communication with the reader.
• First you have to communicate with the reader.
• Second, the reader communicates with the card, acting as the intermediary before sending the data to the card.
• Third, communication with a smart card is based on the APDU format. The card will process the data and return it to the reader, which will then return the data to its originating source.
The following classes are used for communicating with the reader:
• ISO command classes for communicating with 7816 protocol
• Classes for communicating with the reader
• Classes for converting data to a manufacturer-specific format
• An application for testing and using the cards for an intended and specific purpose
Readers come in many forms, factors and capabilities. The easiest way to describe a reader is by the method of its interface to a PC. Smart card readers are available that interface to RS232 serial ports, USB ports, PCMCIA slots, floppy disk slots, parallel ports, infrared IRDA ports and keyboards and keyboard wedge readers. Card readers are used to read data from – and write data to – the smart card. Readers can easily be integrated into a PC utilizing Windows 98/Me, 2000, or XP platforms. However, some computer systems already come equipped with a built-in smart card reader. Some card readers come with advanced security features such as secure PIN entry, secure display and an integrated fingerprint scanners for the next-generation of multi-layer security and three-factor authentication.
Another difference in reader types is on-board intelligence and capabilities. An extensive price and performance difference exists between an industrial strength reader that supports a wide variety of card protocols and the less expensive win-card reader that only works with microprocessor cards and performs all processing of the data in the PC.
The options in terminal choices are just as varied. Most units have their own operating systems and development tools. They typically support other functions such as magnetic-stripe reading, modem functions and transaction printing.
To process a smart card the computer has to be equipped with a smart card reader possessing the following mandatory features:
• Smart Card Interface Standard – ISO 7816 is an international standard that describes the interface requirements for contact-type smart cards. These standards have multiple parts. For instance, part 1, 2 and 3 are applicable to card eaders. Part 1 defines the physical characteristics of the card. Part 2 defines dimension and location of smart card chip contacts. Part 3 defines the electronic signals and transmission protocols of the card. Card readers may be referred to as conforming to ISO 7816 1/2/3, or in its simplified term, ISO 7816.
• Driver – This refers to the software used by the operating system (OS) of a PC for managing a smart card and applicable card reader. To read a smart ID card, the driver of the card reader must be PC/SC compliant which is supported by most card reader products currently available. It should be noted that different OS would require different drivers. In acquiring card readers, the compatibility between the driver and the OS has to be determined and ensured.

Desirable Features in a Smart Card Reader
Card Contact Types refers to how the contact between a card reader and a smart card is physically made. There are two primary types of contact: landing contact and friction contact (also known as sliding or wiping). For card readers featuring friction contact, the contact part is fixed. The contact wipes on the card surface and the chip when a card is inserted. For card readers featuring the landing type, the contact part is movable. The contact "lands" on the chip after a card is wholly inserted. In general, card readers of the landing type provide better protection to the card than that of the friction type.
Smart card readers are also used as smart card programmers to configure and personalize integrated circuit cards. These programmers not only read data, but also put data into the card memory. This means that not only CPU based smart cards, but also simple memory cards can be programmed using a smart card reader. Of course the card reader must support the appropriate protocol such as the asynchronous T=0, T=1 or synchronous I2C protocols.
It won't take long before smart card readers become an integral part of every computer – and, subsequently, the lives of computer users. Computer systems with keyboards that have smart card reader/writer integration are also available.
Smart card readers are also accessible in the form of USB dongle. USB dongles are frequently used with GSM phones, which contain a SIM smart card. Additionally, phone numbers can be edited on a PC using the USB smart card dongle.

Key features and characteristics of smart cards
Cost: Typical costs range from $2.00 to $10.00. Per card cost increases with chips providing higher capacity and more complex capabilities; per card cost decreases as higher volume of cards are ordered.
Reliability: Vendors guarantee 10,000 read/write cycles. Cards claiming to meet International Standards Organization (ISO) specifications must achieve set test results covering drop, flexing, abrasion, concentrated load, temperature, humidity, static electricity, chemical attack, ultra-violet, X-ray, and magnetic field tests.
Error Correction: Current Chip Operating Systems (COS) perform their own error checking. The terminal operating system must check the two-byte status codes returned by the COS (as defined by both ISO 7816 Part 4 and the proprietary commands) after the command issued by the terminal to the card. The terminal then takes any necessary corrective action.
Storage Capacity: EEPROM: 8K - 128K bit. (Note that in smart card terminology, 1K means one thousand bits, not one thousand 8-bit characters. One thousand bits will normally store 128 characters - the rough equivalent of one sentence of text. However, with modern data compression techniques, the amount of data stored on the smart card can be significantly expanded beyond this base data translation.)
Ease of Use: Smart cards are user-friendly for easy interface with the intended application. They are handled like the familiar magnetic stripe bank card, but are a lot more versatile.
Susceptibility: Smart cards are susceptible to chip damage from physical abuse, but more difficult to disrupt or damage than the magnetic stripe card.
Security: Smart cards are highly secure. Information stored on the chip is difficult to duplicate or disrupt, unlike the outside storage used on magnetic stripe cards that can be easily copied. Chip microprocessor and Co-processor supports DES, 3-DES, RSA or ECC standards for encryption, authentication, and digital signature for non-repudiation.
First Time Read Rate: ISO 7816 limits contact cards to 9600 baud transmission rate; some Chip Operating Systems do allow a change in the baud rate after chip power up; a well designed application can often complete a card transaction in one or two seconds. Speed of Recognition Smart cards are fast. Speed is only limited by the current ISO Input/Output speed standards.
Proprietary Features: These include Chip Operating System (COS) and System Development Kits.
Processing Power: Older version cards use an 8-bit micro-controller clockable up to 16 MHz with or without co-processor for high-speed encryption. The current trend is toward customized controllers with a 32-bit RISC processor running at 25 to 32 MHz.
Power Source: 1.8, 3, and 5 volt DC power sources.
Support Equipment Required for Most Host-based Operations: Only a simple Card Acceptance Device (that is, a card reader/writer terminal) with an asynchronous clock, a serial interface, and a 5-volt power source is required. For low volume orders, the per unit cost of such terminals runs about $150. The cost decreases significantly with higher volumes. The more costly Card Acceptance Devices are the hand-held, battery-operated terminals and EFT/POS desktop terminals.

Why consider smart cards?
IF a portable record of one or more applications is necessary or desirable, AND
Records are likely to require updating over time, Records will interface with more than one automated system, Security and confidentiality of records is important
THEN, smart cards are a feasible solution for making data processing and transfer more efficient and secure.
Advantages of Smart Cards:
• The capacity provided by the on-board microprocessor and data capacity for highly secure, off-line processing
• Adherence to international standards, ensuring multiple vendor sources and competitive prices
• Established track record in real world applications
• Durability and long expected life span (guaranteed by vendor for up to 10,000 read/writes before failure)
• Chip Operating Systems that support multiple applications
• Secure independent data storage on one single card
Barriers to Acceptance of Smart Cards:
• Relatively higher cost of smart cards as compared to magnetic stripe cards. (The difference in initial costs between the two technologies, however, decreases significantly when the differences in expected life span and capabilities- particularly in terms of supporting multiple applications and thus affording cost sharing among application providers- are taken into account).
• Present lack of infrastructure to support the smart card, particularly in the U.S., necessitating retrofitting of equipment such as vending machines, ATMs, and telephones.
• Proprietary nature of the Chip Operating System. The consumer must be technically knowledgeable to select the most appropriate card for the target application.
• Lack of standards to ensure interoperability among varying smart card programs.
• Unresolved legal and policy issues related to privacy and confidentiality or consumer protection laws.

Smart Card Applications
Financial Applications
• Electronic Purse to replace coins for small purchases in vending machines and over-the-counter transactions.
• Credit and/or Debit Accounts, replicating what is currently on the magnetic stripe bank card, but in a more secure environment.
• Securing payment across the Internet as part of Electronic Commerce.
Communications Applications
• The secure initiation of calls and identification of caller (for billing purposes) on any Global System for Mobile Communications (GSM) phone.
• Subscriber activation of programming on Pay-TV.
Government Programs
• Electronic Benefits Transfer using smart cards to carry Food Stamp and WIC food benefits in lieu of paper coupons and vouchers.
• Agricultural producer smart marketing card to track quotas.
Information Security
• Employee access cards with secured passwords and the potential to employ biometrics to protect access to computer systems.
Physical Access Control
• Employee access cards with secured ID and the potential to employ biometrics to protect physical access to facilities.
Transportation
• Drivers Licenses.
• Mass Transit Fare Collection Systems.
• Electronic Toll Collection Systems.
Retail and Loyalty
• Consumer reward/redemption tracking on a smart loyalty card, that is marketed to specific consumer profiles and linked to one or more specific retailers serving that profile set.
Health Care
• Consumer health card containing insurance eligibility and emergency medical data.
Student Identification
• All-purpose student ID card (a/k/a campus card), containing a variety of applications such as electronic purse (for vending machines, laundry machines, library card, and meal card).

How to Selecting a Video Cable

2011-01-22T02:19:00.005+05:30

Selecting Video Cable
There are two factors that govern the selection of cable: the location of cable runs, either indoor or outdoor, and the maximum length of the individual cable runs.
Video coaxial cable is designed to transmit maximum signaling energy from a 75 ohm source to a 75 ohm load with minimum signal loss. Excessive signal loss and reflection occurs if cable rated for other than 75 ohms is used. Cable characteristics are determined by a number of factors (core material, dielectric material and shield construction, among others) and must be carefully matched to the specific application. Moreover, the transmission characteristics of the cable will be influenced by the physical environment through which the cable is run and the method of installation.
Use only high quality cable and be careful to match the cable to the environment (indoor or outdoor). Solid core, bare-copper conductor is best suited to video applications, except where flexing occurs. In locations where the cable must be continuously flexed (i.e., when used with scanners or pan & tilts), use cable intended for such movement. This cable will have a stranded wire core. Use only cable with pure copper stranding. Do not use cable with copper-plated steel stranding because it does not transmit effectively in the frequency range used in CCTV.
The preferred dielectric material is foam polyethylene. Foam polyethylene has better electrical characteristics and offers the best performance over solid polyethylene, but it is more vulnerable to moisture. Use cable with solid polyethylene dielectric in applications subject to moisture.
In the average CCTV installation, with cable lengths of less than 750 feet (228 m),RG59/U cable is a good choice. Having an outside dimension of approximately 0.25 inches, it comes in 500-and 1,000-foot rolls.
For short cable runs, use RG59/U with a 22-gauge center conductor, which has a DC resistance of about 16 ohms per 1,000 feet (304 m). For longer runs, the 20-gauge variety which has a DC resistance of approximately 10 ohms per 1,000 feet will work well. In either case, cables with polyurethane or polyethylene as the dielectric material are readily available.
For installations requiring cable runs between 800 (244 m) and 1,500 feet (457 m),RG6/U is best. Having the same electrical characteristics as RG59/U, its outer dimension also is about equal to that of RG59/U.RG6/U comes in 500-,1000-and 2000-foot rolls, and it may be obtained in a variety of dielectric and outer-jacket materials. Due to its large-diameter center conductor of about 18 gauge,RG6/ U has a DC resistance of approximately 8 ohms per 1,000 feet (304 m) and can deliver a signal farther than RG59/U.
Use RG11/U to exceed the capability of RG6/U. Once again, the electrical characteristics of this cable are basically the same as the others. The center conductor can be ordered in 14-or 18-gauge sizes, producing a DC resistance of approximately 3-8 ohms per 1,000 feet (340 m). Being the largest of the three cables at 0.405 inches, it is more difficult to handle and install.RG11/U cable usually is delivered in 500-,1000-and 2000-foot rolls.
Because of special applications, variations of RG59/U, RG6/U and RG11/U frequently are introduced by manufacturers.
Due to changes in fire and safety regulations throughout the country, Teflon and other fire-retardant materials are becoming more popular as outer-jacket and dielectric materials. In case of a fire, these materials do not give off the same poisonous fumes as PVC-type cables, and therefore, are considered safer.
For underground applications, direct burial cables, made specifically for that purpose are recommended. The outer jacket of this type of cable contains moisture-resisting and other materials that protect the cable, allowing it to be placed directly into a trench.
With numerous choices available, finding the right video cable for each camera application should be easy. After the installation has been properly assessed, read the equipment specifications and complete the appropriate calculations.

Cable Runs
coax cable has built-in losses, the longer and smaller the cable is, the more severe the losses become; and the higher the signal frequency, the more pronounced the losses. Unfortunately this is one of the most common and unnecessary problems currently plaguing CCTV security systems as a whole.
If, for example, your monitor is located 1,000 feet (304 m) from the camera, approximately 37-percent(37%) of the high frequency information will be lost in transmission. The unfortunate aspect of this condition is that it is not obvious. You cannot see information that is not there and may not even realize that information has been deleted. Because many CCTV security systems have cable runs that exceed several thousand feet, unless you are aware of this characteristic of cable, your system may be providing a seriously degraded image.
So, if your cameras and monitors are separated by lengths greater than 750 feet (228 m), you should check to make certain that some provision has been made to guarantee the video signal's transmission strength.
Cable Type* RG59/U = 750 ft.
Cable Type* RG6/U = 1,000 ft.
Cable Type* RG11/U = 1,500 ft.
* = Minimum cable requirements= 75 ohms impedance, All-copper center conductor, All-copper braided shield with 95% braid coverage.

Cable Termination
In video security systems, camera signals must travel from the camera to the monitor. The method of transmission is usually "coax" cable. Proper termination of cables is essential to a system's reliable performance.
Because the characteristic impedance of coax cable ranges from 72 to 75 ohms, it is necessary that the signal travels on a uniform path along any point in the system to prevent any picture distortion and to help ensure proper transfer of the signal from the camera to the monitor. The impedance of the cable must remain constant with a value of 75 ohms. To properly transfer power between two video devices with acceptable losses, the signal output from the camera must match the input impedance of the cable, which in turn must match the input impedance of the monitor. The end point of any video cable run must be terminated in 75 ohms. Usually, the cable run will end at the monitor, which will ensure that this requirement is met.
Usually the video input impedance of the monitor is controlled by a switch located near the looping video (input/output) connectors. This switch allows for either 75 ohm termination if the monitor is the "end point",or Hi-Z for looping to a second monitor. Check equipment specifications and instructions to determine the proper termination requirements. Failure to terminate signals properly usually results in a high contrast, slightly grainy picture. Ghosting and other signal imperfections also may be evident.
It important to note that the BNC connectors , which are usually used for terminating coax cable, are manufactured in two different impedance -75 ohm for video use and 50 ohm for radio use. Most shopkeepers are not a ware of this difference so it is better to check the manufacturer's specification before you buy.

Unsaddled twisted pair (UTP)
UTP cabling is both in expensive and ideal for transmission of video signal up to 1350m. the cabling is run to multiplexer that supports the popular RJ45 connector . Legacy cameras with coax connectors can be retrofit with balun (balanced/unbalanced ) adpters allowing the signal to be converted from the coaxial cable (unbalanced ) to twisted pair (balanced) cable. A typical system consists of a transmitter connected to a coax cable or connector which is then converted to a signal suitable for transmitting over twisted pair cable. On the receiving end of the twisted-pair cable is a receiver that converts the signal back to one suitable for transmission on coax cable.
UTP. Requires only one twisted pair cable to carry power, video and control signals , as opposed to three different proprietary cables with traditional CCTV systems.
While the total cost of UTP cabling can be up to 30% less than traditional CCTV systems over the life of the system, it easily accommodates technological advances such as digital integration IP-based networks and power over Ethernet.
Optical fibre is some times used in this environment where distances would require use of repeaters for signal strength or where EMI. (Elector-Magnetic interference) is an issue.

Fibre Optic Cable
While coaxial cable is the most suitable cable for CCTV signal transmission over short distances it is best to consider other mediums for distances greater than 1 kilometer. The most suitable for these distances is fibre optic.
Fibre optic is a fine strand of glass which is highly transparent. There are two main types referred to single mode and multi-optic fibres. The single mode fibre optic has a high level of efficiency but can transmitting only one mode. Laser transmitters an receivers arousal required for single mode application . Multi -mode fibre optics is thicker and can operate in several modes and can accommodate cheaper forms of transmission media such as infrared . These cables are used main lyover shorter distances while the single mode fibre would be used where distance and performance were critical . The main types of applications for fibre optics are:-
Light Guide fiber-used in instrument panels and lamps it carries visible light only.
Coherent fibre-Normally referred to as coherent bundle because of its construction. This glass fibre will carry an undischarged image of light over a short distance. Its ideal for extending the lens with application in covert surveillance. High performance-For CCTV application we tend to use high performance fibers with a signal transmission media. For CCTV application we have to use the latter , high performance fibers. The glass stransparency quality of the glass is a key factor in its ability to transmit light effectively over distances and this is being improved constantly.
Fiber optic system may consist of a standard camera with the video signal being fed into a fibre optic trasmitter. The transmitter consists of circuits to convert the video signal into a series of modulated pulses . These pulses are then fed to the light source that may either be a laser or light emitting diode (LED) which emits a series of light pulses .these light pulses are focused on to the centre core of the cable which acts as a guide to the light passing along the fibre's lenght. The main light passes straight along the centre of the fibre while a little of the light hits the side of the glass tube. This is reflected back into the centre by the cladding.
This results in very low transmission losses over long distances. Fibre optic cable also has the advantage of not being affected by electromagnetic interference or EMI.

Splitting / Amplifying the Video Signal
Video signal used in CCTV equipment is nominally a one volt peak-to-peak signal and is impedance sensitive to 75 ohms for ideal video reproduction at the monitor. If these parameters are not kept, then the video will degrade.
Distribution Amplification
If the installation of a system requires viewing the video at multiple locations from a single camera, there are a few different ways of accomplishing this. One way is through using a distribution amplifier. This device basically takes the single video signal and reproduces the exact signal into multiple outputs; and in the case of the Pelco DA104DT you would get four identical outputs.
So, if the input signal is a one volt peak-to-peak signal you will get four output signals of the same amplitude. Providing the run distance for the type of coax used is kept within the specified length, no other equipment will be needed to reproduce a nice clear video display on each monitor. Another timesaving feature of the Pelco DA104DT is that there are not adjustments required. Just connect the unit, turn it on, and the installation is complete. If the need arises where more than four signals are required, multiple units can be linked together by simply using one of the output signals as an input signal to the next unit, and so on.
Equalizing Amplification
Due to the many factors that can effect the video signal, it is sometimes necessary to enhance the video signal (as in transmitting a nominal video signal level) directly out of the camera, through RG59 coax to a monitor, while still producing a clear video display across the entire length of the coax. In this case the coax should not exceed 750 feet (228 m).
However, let's say you need to use RG59 because it's more flexible and much easier to work with but the cable length must be 1,500 feet (457 m). The signal at this point is going to be weak and will display a very degraded picture on the monitor. As mentioned, there are many things that can effect signal strength before the signal reaches the monitor. If you find a weak signal, simply pass the weak signal through an equalizing amplifier, make the required adjustments, and once again there will be a good, strong signal that will produce a nice picture.
The Pelco model EA2010 is a post-equalizing amplifier which simply means that this device will be located close to the monitor. There's an advantage to this design in that AC power is usually more readily available at the monitoring location than it is somewhere back up the coax line, and with this type of design it only requires one person to view the monitor display while at the same time making the required adjustments to obtain the nominal signal level.
As mentioned in the example on RG59,the signal strength is good up to nominally 750 feet (228 m). With the Pelco EA2010 amplifying the signal, the same grade of coax can be used in runs of up to 3,000 feet (914 m).
In regard to any equalizing amplification system, there is another type of post-equalizing amplifier that Pelco offers. It is the half-duplex post-equalizing amplifier. This device (as far as the amplification of the video signal is concerned) is exactly like the EA2010.The difference is that the EA2000 was designed specifically for use with any of the Pelco Coaxitron® (up-the-coax) control/transmitter systems. This device enables the video signal requiring amplification to be transmitted over the same coaxial cable over which the control signal is transmitted, whereas if you used the EA2010 it would block the Coaxitron® control signal from being transmitted.

Cabling for IP Cameras
IP convergence means attaching different building and communication systems -- such as data, voice, security cameras and building automation systems -- onto a common network through a common Internet protocol. In the surveillance world, IP convergence means moving from analog to IP cameras.
IP camera technology offers new and expanded features in CCTV surveillance that were previously unavailable on analog cameras. However, performance and scalability can be affected because of poor system infrastructure, as well as product performance.
For organizations to realize the full benefits of IP video surveillance, they must design and build a system that is capable of meeting current and future requirements, which includes allocating sufficient bandwidth to video-carrying traffic that will not congest the network. To do this, they must implement a standards-based structured cabling system that will allow future devices to be added, which will save time and money by providing the biggest return on investment.
Cable selection and bandwidth go hand-in-hand. Considerations when selecting the cable media include number of cameras, type of camera, location of the cameras (environment), distance to the telecom rooms, type of termination equipment and whether PoE will be running through the cable or local power will be provided at the device end. Another factor when selecting cable is the length of time planned to occupy the building.
Today’s TIA standards define cabling types, distances, connectors, cable system architectures, cable performance characteristics, pathways, cable installation requirements and methods of testing installed cable to help system designers and installers select the most efficient cabling for each environment. TIA-recognized structured cabling standards recommend twisted pair copper and fiber-optic cable as the preferred media selection for efficient IP network systems. However, security integrators need to be aware of the range of options available and the pros and cons of each.
Coax Cable
Distances using coax cable can be up to 3,000 feet. This cable is most often found when end users would like to use their installed cable plant, which was installed for analog cameras. However, because an IP camera is equipped with an RJ-45 connection, media converters are needed on each end of the coax cable runs.
Using existing coax cable for running Ethernet to IP cameras is a “band-aid” approach and does not comply with TIA. This is a fast solution, but eventually the cabling system will need to change to a structured cabling system -- through twisted pair or fiber -- especially when higher bandwidth megapixel cameras are required. Running Ethernet over coax is limited to less than 1 GB transmissions. Therefore, as the bandwidth increases on both the camera and the traffic running through the network, coax cable capabilities will be limited.
Twisted Pair
Unshielded or shielded twisted pair cable provides many benefits over coax. Twisted pair, with its RJ connection, allows immediate attachment to the camera. One of the biggest benefits is that twisted pair can provide power over the same cable, eliminating local power at the device end.
There are basically two grades of UTP cable: Cat-5e (100 MHz) and Cat-6 (250 MHz). A Cat-5e cable may be sufficient with its allowable 1 GB/s data rate (depending on the protocol), but Cat-6 operates at a higher data rate (up to 10 GB/s). Because of its improved transmission performance and superior immunity from external noise, systems operating over Cat-6 cabling will have fewer errors than Cat-5e. And, when inducing noise or heat -- such as in PoE and PoE Plus -- Cat-6 has been proven to operate with no latency or fear of dropped packets.
Standards-based twisted pair cabling is limited to 100 meters between the device and the termination point, such as a consolidation point or telecommunications room. The chart on the following page provides cable options for selecting cable based on distance and power. Twisted pair can actually provide a signal farther than 100 meters through active equipment, but this would not meet the TIA standards and therefore would not work if the analog camera is to be replaced with an IP camera.
Fiber-optic Cable
The answer to the distance challenge is fiber-optic cable. Fiber-optic cable can easily operate IP cameras through media conversion, allowing twisted pair patch cords or horizontal UTP cable runs to connect directly to the device and to the terminating equipment in the TR. Even coax-based analog cameras can use fiber-optic cable, but this entails deploying multiplexers in addition to media converters, which can become costly per channel.
Fiber-optic cable’s other advantages include its small diameter and biggest bandwidth carrying capacity. Fiber-optic cable is immune to electrical interference, which makes it ideal for harsh environments such as lightning, power plants and industrial manufacturing. In addition, fiber optic is a more secure signal -- because it is harder to tap into.
Since power cannot run through glass, fiber-optic cable cannot directly carry PoE. But it can be jacketed with copper conductors in the form of a composite cable. Certain cables on the market provide Ethernet to be carried through fiber strands while power runs through stranded copper conductors. Distances up to 3,850 feet can be achieved. Because the cable carries lowvoltage power -- up to 25 watts as defined by PoE Plus and IEEE 802.3at -- this cable is actually defined as a Class 3 copper cable with fiber. The total distance is limited by the media power provided through the active media converter on the termination side, as well as the gauge of the copper. The more power needed, the thicker the gauge.

Challenging Decisions and Changing Standards
Security camera locations vary depending on each installation. When the TIA standards were written, the devices in work areas consisted of telephones, modems, data terminals, fax machines and desktop computers. Although the TIA standards originally applied to data and voice Ethernet applications, mainly in office environments, they were written to be modular, providing scalability for adding IP devices. However, electronic safety and security devices, particularly surveillance equipment, create unique challenges, mainly due to environmental factors.
The BICSI organization, together with ANSI, is currently reviewing the existing standards and has created a standards group to focus solely on physical infrastructure for ESS devices. To be designated “ANSI/BICSI 005” upon completion, this standard will define cabling design and installation requirements, as well as provide recommendations specific to ESS systems, including surveillance, access control, paging, signage, and even fire detection and alarm systems.
The standard also will provide information for access control, intrusion detection and surveillance systems, as well as guidance on other topics, such as meeting the IP needs of fire detection and alarm systems. And as more and more devices find their way to the network, the selection of cabling and physical infrastructure becomes more critical.

Now we are discussed about coaxial cable's Construction
RG59/U, RG6/U and RG11/U is circular. Each has a center conductor surrounded by dielectric insulating material, which in turn is covered by a braid to shield against electromagnetic interference. The outer covering is the jacket.

The coaxial cable's two conductors are separated by a nonconductive or dielectric material. The outer conductor (braid) acts as a shield and helps isolate the center conductor from spurious electromagnetic interference. The outer covering helps physically protect the conductors.

Center Conductor:
For CCTV applications, solid copper conductors are required, which is carrying a video signal. Center conductor comes in varying diameters usually ranging from 14 gauge to 22 gauge. The structure of the center conductor generally is solid copper or copper-clad steel, designated as bare copper weld or BCW. For CCTV applications, solid copper conductors are required. Copper clad, copper weld, or BCW cables have much greater loop resistance at baseband video frequencies and should never be used for CCTV. To determine the type, look at the cut end of the center conductor. Copper clad cable will be silver in the center intead of copper all the way through. Variation in the size of the center conductor has an overall effect on the amount of DC resistance offered by cable. Cables which contain large diameter center conductors have lower resistances than cables with smaller diameters. This decreased resistance of large diameter cable enhances the ability of a cable to carry a video signal over a longer distance with better clarity, but is also more expensive and harder to work with.

For applications where the cable may move up/down or side-to-side, select cable that has a center conductor consisting of many small strands of wire. As the cable moves, these strands flex and resist wear due to fatigue better than a cable with a solid center conductor.

Dielectric Insulating Material
Center conductor is an evenly made dielectric insulating material which is available in some form of either polyurethane or polyethylene. This dielectric insulator helps determine the operating characteristics of coax cable by maintaining uniform spacing between the center conductor and its outer elements over the entire length of the cable. Dielectrics made of cellular polyurethane or foam are less likely to weaken a video signal than those made with solid polyethylene. This lower attenuation is desirable when calculating the loss/length factor of any cable. Foam also gives a cable greater flexibility, which may make an installer's job easier. Although foam dielectric material offers the best performance, it can absorb moisture, which will change its electrical behavior.

Because of its rigid properties, solid polyethylene maintains its shape better than foam and withstands the pressures of accidental pinching or crimping, but, this characteristic also makes it slightly more difficult to handle during installation. In addition, its loss/length attenuation factor is not quite as good as foam, which should be considered in long cable runs.

Braid or Shield
Cables using aluminum foil shielding or foil wrap material are not suitable for CCTV installations. Wrapped around the outside of the dielectric material is a woven copper braid (shield), which acts as a second conductor or ground connection between the camera and the monitor. It also acts as a shield against unwanted external signals commonly called electromagnetic interference or EMI, which may adversely affect a video signal.

The amount of copper or wire strands in the braid deter- mine how much EMI it keeps out. Commercial grade coax cables containing loosely woven copper braid have shielding coverages of approximately 80%. These cables are suitable for general purpose use in applications where electrical interference is known to be low. They also work well when the cable is to be installed in metal conduit or pipe, which also aids in shielding.

If you are not sure of the conditions and are not running pipe to screen out more EMI, use a cable with a "maximum shield" or heavy braid--type cable containing more copper than those of commercial grade coax. This extra copper obtains the higher shielding coverage by having more braid material made in a tighter weave. For CCTV applications, copper conductors are needed.

Cables using aluminum foil shielding or foil wrap material are not suitable for CCTV work. Instead, they usually are intended to transmit radio frequency signals such as those employed in transmitter systems or in master antenna distribution systems.

Aluminum or foil cable may distort a video signal to such a point that signal quality may be far below the level required for proper system operation, especially over long cable runs, and therefore not recommended for CCTV use.

Outer Jacket
The last component comprising a coax cable is the outer jacket. Although other materials are used, polyvinyl chloride, or PVC, is commonly used in its construction. Available in many colors such as black, white, tan, and gray, the jacket lends itself to both indoor and outdoor applications.

Newly developed some Video & Power Combination Cable is there in market.
This combination cable featuring BNC to BNC video connectors and 2.1mm DIN male & female for power supply connection. A BNC to RCA adapter is also included. Also included are two pigtails to allow breakout of power connectors to use with screw terminal power supplies and cameras. This cable is available in 50 foot and 100 foot lengths. Maximum distance for DC power should not exceed 100 feet.

Specials thanks to all of Manufacturers, Suppliers & Exporters to provide the information.

Importance of CCTV

2011-01-16T21:49:00.000+05:30

The full form of CCTV is Closed Circuit Television Cameras. These cameras can be fitted just about anywhere with the help of a simple process. Once set up, they help to record all the activities that are taking place in a specific area unless switched off or disabled. They are quite compact in size and are not really instantly visible to everyone. CCTV’s vary greatly in terms of the picture and sound quality that they can provide to their users. They may be colored or black and white. Some of them may show very clear pictures while others may showcase slightly hazy or disturbed videos. Thus, it is vital to choose carefully while buying CCTV cameras. CCTV cameras come with the following benefits and their importance cannot be undermined.

1.CCTV cameras are very useful in combating terrorism. This is because it is simply not practically possible to deploy police forces in every conceivable public area to look out for strange behavior from people or the placement of strange, unclaimed objects. CCTV cameras can look out for such things and prevent acts of terrorism before they have a chance to take place. The images captured on these cameras are transmitted to a central location where they are observed by the concerned person.

2.CCTV cameras are of unprecedented importance in the field of sporting. Some of them come equipped with high technology that helps to make crucial and difficult decisions in a game or match. Every single moment of play is recorded to be used later on too for making improvements.

3.CCTV cameras, if installed in a house or building, can help combat burglaries and thefts to a large extent. Just the knowledge about the existence of such cameras is enough to deter the possible intruders who may try to do away with your things at an available opportunity. CCTV’s can record footage and send it to another system over the internet. This can be done live or later on after the day has passed. So, it can help prevent burglaries and locate criminals whose faces may have been captured.

4.CCTV cameras are of great importance in places of work. They help establish a means of control and a system of keeping checks on the employees. If the employees are found to be wanting in a certain area, the requisite steps to correct this are taken by the management.

5.CCTV cameras in public places discourage vandalism and destruction of public property as the people involved in doing so know that they are being observed. Merely the existence of these cameras greatly improves the law and order situation of a city.

6.These cameras help keep a check on your babysitter’s method of working in case you have children and are worried about leaving them all alone with a stranger. You can be assured that your child is in safe hands and make changes if you find the nanny hired by you as incompetent in any way.

Uses of CCTV in India?
* CCTV provides a deterrent to crime and vandalism.
* CCTV system enables 24 hour monitoring of all the designated areas.
* CCTV security cameras enables in clear identification of miscreants within the range of the CCTV cameras.
* To provide continuous recording of all CCTV cameras in the system.
* To enable rapid movement of any CCTV camera to pre-set positions of pan, tilt and zoom.
* To provide independent viewing of any CCTV camera at the controlling station.
* To enable live, real time recording of selected CCTV cameras.
* CCTV systems can be used to remotely or locally monitor following areas- Finance and banking, Parking areas, Educational Institutions, Jewellery showrooms, Storage godowns and warehouses, Construction sites, Gas stations, Commercial buildings, Hospitals, Shopping complexes and malls, Manufacturing plants, Transporting companies.

CCTV system should be used at offices, factories, restaurants, shops, workshops, schools, colleges, hospitals, airports, banks, malls, industrial and comercial spaces.

Electronic Access Control Systems: A Global Strategic Business Report

2011-01-11T21:36:00.001+05:30

Global Electronic Access Control Systems Market to Reach US$6.0 Billion by 2015, According to New Report by Global Industry Analysts, Inc.

GIA announces the release of a comprehensive global report on Electronic Access Control Systems. Although the prolonged severity of the recent economic slowdown, and depressed key end-use sectors have elicited decline in value sales for electronic access control systems (EACS), the market is nevertheless expected to recover poise in the short to medium term period to reach US$6.0 billion by 2015. Primary factors fingered to drive this growth include increasing concerns over safety and security among individuals and organizations, post recession resurgence in key end-use markets and technology developments. Robust growth in demand from developing markets, particularly Asia-Pacific also augurs well for the market.
By product, Card-Based Electronic Access control systems market continues to be the largest product segment, holding a lion’s share of the global market. Smart cards represent the largest revenue contributor to the card-based EACS market. Audio and Video-Based Electronic Access Control Systems market is the fastest growing product segment, waxing at a CAGR of about 6.8% over the analysis period Major players in the marketplace include Aiphone Co. Ltd., ASSA ABLOY AB, BIO-key, International Inc., DigitalPersona Inc, Gunnebo Ab, Hirsch Electronics Corporation, Honeywell Access Systems, Ingersoll Rand Recognition Systems Inc., Linear LLC, Imprivata® Inc., Kaba Holding AG, L-1 Identity Solutions, NAPCO Security Systems Inc., PAC International Ltd, SAFRAN Group, SecuGen Corporation, Siemens Industry USA Building Technologies, The Chamberlain Group Inc, UTC Fire & Security, Chubb Securite S.A.S, and GE Security Inc.

http://www.gobeyondsecurity.com/forum/topics/electronic-access-control

What is the difference between "biometric identification" and "biometric verification"?

2011-01-09T16:11:00.001+05:30

What is the difference between "biometric identification" and "biometric verification"?

BIO-key employs fingerprint biometrics to perform true user identification. When exploring biometric security or any other form of security, it is important to understand the difference between identification and verification.

Biometric identification technology allows users to prove their identity by submitting a biometric sample, such as a fingerprint, iris scan or voice pattern. No other identification data is provided; identification is achieved through biometrics alone.

Non-biometric technologies authorize users via a key, card or identification code such as a PIN or password. Biometric verification technology adds a biometric sample to the mix, along with the identification code or key. These systems can be defeated easily by obtaining or counterfeiting the key, card or password.

Among automated biometric systems, only those that are capable of real-time identification can eliminate the possibility of duplicates in a database.
Biometric identification compares a biometric "signature" to all the records stored in a database to determine if there is a match. Because it requires comparing each existing record in the database against the new biometric characteristic, it can be slow and is usually not suitable for real-time applications such as access control or time and attendance.

You'll find biometric identification used most frequently in such applications as law enforcement — for instance, the comparison of a fingerprint from a crime scene to a database of prints collected from convicted criminals.

Biometric verification compares a newly-scanned biometric characteristic to a measurement previously collected from that same person to verify that individual's identity. For instance, when an employee is hired, that employee's fingerprint will be enrolled into the company's biometric time and attendance system. When that employee attempts to clock in the next day, her newly-scanned fingerprint will be compared to the fingerprint scan collected when she was enrolled into the system. If there is a match, the employee's punch will be recorded.

Because of this one-to-one comparison, biometric verification systems are generally much faster than biometric identification systems. Most commercial applications of biometrics for time and attendance or access control use biometric verification.

All about CCTV Lenses

2010-11-13T20:45:00.028+05:30

We already discuss about CCTV lenses so, we have the basic idea now we learning in details:

The human eye is an incredibly adaptable device that can focus on distant objects and immediately refocus on something close by. It can look into the distance or at a wide angle nearby. It can see in bright light or at dusk, adjusting automatically as it does so. It also has a long ‘depth of field’; therefore, scenes over a long distance can be in focus simultaneously. It sees colour when there is sufficient light, but switches to monochrome vision when there is not. It is also connected to a brain that has a faster updating and retentive memory than any computer. Therefore, the eyes can swivel from side to side and up and down, retaining a clear picture of what was scanned. The brain accepts all the data and makes an immediate decision to move to a particular image of interest, select the appropriate angle of view and refocus. The eye has another clever trick in that it can view a scene of great contrast and adjust only to the part of it that is of interest.

By contrast, the basic lens of a CCTV camera is an exceptionally crude device. It can only be focused on a single plane, everything before and after this plane becoming progressively out of focus. The angle of view is fixed. At any time, it can only view a specific area that must be predetermined. The iris opening is fixed for a particular scene and is only responsive to global changes in light levels. Even an automatic iris lens can be only be set for the overall light level, although there are compensations for different contrasts within a scene. Another problem is that a lens may be set to see into specific areas of interest when there is much contrast between these and the surrounding areas. However, as the sun and seasons change so do light areas become dark and dark areas become light. The important scene can be ‘whited out’ or too dark to be of any use.

A controversial but important aspect of designing a successful CCTV system is the correct selection of the lens. The problem is that the customer may have a totally different perspective of what a lens can see compared to the reality. This is because most people perceive what they want to view as they see it through their own eyes. Topics such as identification of miscreants or numberplates must be subjects debated frequently between installing companies and customers.

The selection of the most appropriate lens for each camera must frequently be a compromise between the absolute requirements of the user and the practical use of the system. It is just not possible to see the whole of a large loading bay and read all the vehicle number plates with one camera. The solution may be more cameras or viewing just a restricted area of particular interest. A Company putting forward the system proposal should have no hesitation in pointing out the restrictions that may be incurred according to the combination of lens versus the number of cameras. Better this than an unhappy customer who is reluctant to pay the invoice.

Although a lens is crude compared to the human eye, it incorporates a high degree of technology and development. There can be a large variation in the quality between different makes and this should be considered according to the needs of a particular installation. The lens is the first interface between the scene to be viewed and the eventual picture on the monitor. Therefore, the quality of the system will be very much affected by the choice of lens. For general surveillance of, for instance, a small retail shop, it is possible to use a lower quality lens with quite acceptable results. As the demands of the system requirement increase then the use of a premium quality lens must be considered. The difference in cost between a poor quality and a high quality lens will be a very small percentage of the total cost of a large industrial system.

The CCTV Lens Exposure Control
The exposure in a normal photographic camera can be controlled by a combination of shutter speed and iris opening. This is not so with a CCTV camera lens. A standard CCTV camera produces a complete picture every 1/2 of the mains frequency. This is every 1/25 second where the mains frequency is 50 Hz (cycles per second) and every 1/30 second where the mains frequency is 60 Hz. Generally the exposure time is fixed and the only control of the amount of light passing to the imaging device is by adjusting the size of the iris. This is covered in more detail later in this chapter. Most camera tubes and imaging devices have some tolerance of the amount of light passed by the lens to create an acceptable picture. The range of tolerance is generally inversely proportional to the sensitivity of the camera. The more sensitive cameras require greater control of the iris aperture.

Types of Lenses
Lens Formats

Diagram 1 Types of Lens Mounts

Early CCTV lenses were designed for the 1” format tube camera and many of these are still available on the market. The lens screw thread on these cameras is called a C-mount. This is a particular design of thread size and flange length originally used on photographic cameras. In recent years lenses have been developed for the 2/3”, 1/2” and now 1/3” format cameras. Consequently, great care must be exercised when selecting a lens for a particular camera. Just as there are four formats of camera so there are four formats of lenses and they are not compatible in every combination. A lens designed for a larger format camera may be used on a smaller format but not the reverse. In addition, the field of view will not be the same on different size cameras. There is now a further complication in that there is a range of lenses with what is called the CS-mount. The difference between the two types of mount is the flange back length, which is the distance from the back flange of the lens to the face of the sensor. See diagram 4.1. The screw thread and shoulder length for each type of mount is identical. This makes it impossible to see the difference except that the overall size of the CS-mount lens is generally smaller. A C-mount lens may be used on a CS-mount camera with an adapter ring but a CS-mount lens cannot be used on a C-mount camera. The main problem is that either type of lens can be screwed onto both types of camera without apparent damage. The result is that if the wrong type is used it will be impossible to focus the camera. Some C-Mount lenses have a projection at the back that could damage the sensor in a CS-Mount camera.
Below chart is provided at the end of this chapter showing the relationships between different lenses and camera combinations and the associated angle of view. At the time of going to press, most lenses with a focal length of 25mm and above are still designed for 1” cameras. This means that special care must be taken when using this long focal length lens on modern cameras. For instance, a 25mm 1” lens provides the following approximate angles of view on the different formats. Therefore, there would be a significant variation in the expected scene content if this fact were overlooked.
FORMAT 1" -- ANGLE OF VIEW 29°
FORMAT 2/3" -- ANGLE OF VIEW 9.5°
FORMAT 1/2" -- ANGLE OF VIEW 11.4°
FORMAT 1/3" -- ANGLE OF VIEW 9.79°

How to select a Lens
There are two other main factors that must be considered when selecting the most appropriate lens for a particular situation. The focal length and the type of iris control. Within each of these factors, there are other features that will also need to be considered. Lenses may be obtained with all combinations of focal length and iris control. The selection will depend on the site and system requirement.
Focal Length
The focal length of a lens determines the field of view at particular distances. This can either be calculated from the formula given later in this chapter or found from tables provided by most lens suppliers. Most manufacturers also provide simple to use slide or rotary calculators that computes the lens focal length from the scene size and the object distance. The longer the focal length the narrower is the angle of view. Although not strictly correct, lenses with a focal length longer than 25mm are often called zoom lenses. The focal length of the lens requires careful selection to ensure that the correct area is in view and that the degree of detail is acceptable. A rule of thumb is that to ‘see’ a person on a monitor they should represent at least 10% of the screen height. To ‘see’ in this context means to be able to decide that it is a person. For purposes of being able to identify a known person requires them to be at least 50% of the screen height and preferably 60%. An unknown person should occupy at least 120%of the screen height.
Fixed Focal Length
This type of lens is sometimes called a monofocal lens. As the name implies, it is specified when the precise field of view is fixed and will not need to be varied when using the system. The angle of view can be obtained from the supplier’s specification or charts provided. They are generally available in focal lengths from 3.7mm to 75mm. Longer focal lengths may be produced by adding a 2x adapter between the lens and the camera. It should be noted that this would increase the f-number by a factor of two (reducing the amount of light reaching the camera). If focal lengths longer than these are required, it will be necessary to use a zoom lens and set it accordingly.
Except for very wide-angle lenses, other lenses have a ring for adjusting the focus. In addition, cameras include a focusing adjustment that moves the imaging device mechanically relative to the lens position. This is to allow for minor variations in the back focal length of lenses and manufacturing tolerances in assembling the device in the camera. Correct focusing requires setting of both these adjustments. The procedure is to decide the plane of the scene on which the best focus is required and then set the lens focusing ring to the mid position. Then set the camera mechanical adjustment for maximum clarity. Final fine focusing can be carried out using the lens ring.
The mechanical focusing on cameras is often called the back focus, originally because a screw at the back of the camera moved the tube on a rack mechanism. Modern cameras now have many forms of mechanical adjustment. Some have screws on the side or the top, some still at the back. There are cameras that have a combined C/CS-mount on the front that also has the mechanical adjustment and can accept either type of lens format. The longer the focal length of the lens the more critical is the focusing. This is a function of depth of field described later in this chapter.
Manual Zoom Lens
A zoom lens is one in which the focal length can be varied manually over a range. Usually this is by means of a knurled ring on the lens body. It has the connotation of ‘zooming in’ and therefore infers a lens with a longer than normal focal length. (Say more than 25mm.) The zoom ratio is stated as being for instance 6:1, which means that the longest focal length is six times that of the shortest. The usual way of describing a zoom lens is by the format size, zoom ratio and the shortest and longest focal lengths. For example, 2/3”, 6:1, 12.5mm to 75mm. Again, great care must be taken in establishing both the camera and the lens format. The lens just described would have those focal lengths on a 2/3” camera but an equivalent range of 8mm to 48mm on a 1/2” camera.
Variable Focal Length
This is a design of lens that has a limited range of manual focal length adjustment. It is strictly not a zoom lens because it has quite a short focal length. They are usually used in internal situations where a more precise adjustment of the scene in view is required which may fall between two standard lenses. They are also useful where for a small extra cost one lens may be specified for all the cameras in a system. This saves much installation time and the cost of return visits to change lenses if the views are not quite right. For companies involved in many small to medium sized internal installations such as retail shops and offices this can save on stock holding. It makes the standardisation of systems and costing much easier.
Motorised Zoom Lens
Manual zoom lenses are not widely used in CCTV systems because the angle of tilt of the camera often needs to be changed as the lens is zoomed in and out. The most common need for a zoom lens is where used with a pan tilt unit. The lens zoom ring is driven by tiny DC motors and operated from a remote controller.
With the development of ever-smaller cameras and longer focal length lenses the method of mounting the camera/lens combination must be considered. There are many cases where the lens is considerably larger than the camera and it may be necessary to mount the lens rigidly with the camera supported by it. In other cases, it may be necessary to provide rigid supports for both camera and the lens. Always check the relationship between the camera and lens sizes and weights when selecting a housing or mounting. Most manufacturers of housings can provide lens supports as an accessory.
Focussing A Zoom Lens
The most frequent reason for the focus changing when zooming is that the mechanical focus of the camera has not been set correctly. The following is the procedure for setting up the focus on a camera fitted with a zoom lens.
The focusing ring should be marked ‘near’ and ‘far’. Set this to ‘far’ and set the zoom ring to the widest angle of view. Aim the camera at an object about 40 metres away and adjust the camera focus for maximum clarity. Next zoom in to an object nearby and set the lens focus for maximum clarity. It should now be possible to zoom all the way back without the focus changing. Many motorised zoom lenses will be used in external conditions with limited light. If this is the case then it is advisable to fit a neutral density filter in front of the lens to make the iris open fully. A neutral density filter is one that reduces the amount of light that enters the lens, evenly over the whole of the visible spectrum. This will create the shortest depth of field and ensure setting up more accurately for the worst conditions. The depth of field, as explained later, depends on the aperture opening.
Some controllers can override the automatic iris mechanism, usually to open it to see into darker areas. This is often the case when a camera is looking out over open country in bright sunlight and the lens closes because it measures the average light levels. The scene at ground level can be very dark in these conditions, with little detail. This is not a desirable feature to include unless absolutely necessary. This is because the override can be forgotten with resultant poor pictures being recorded if the system is not fully monitored. The better solution is to tilt the camera down until there is less proportion of sky in the picture.
Motorised Zoom Lenses With pre-sets
There are many situations where it is required to pan, tilt, and zoom to a predetermined position within the area being covered. It is possible to obtain motorised lenses with potentiometers fitted to the zoom and focusing mechanisms. These cause the lens to zoom automatically and focus to the setting by measuring the voltage across the potentiometer and comparing it with the signals in the control system. All other functions are as for motorised zoom lenses. Pre-set controls are only possible with telemetry controlled systems. The specification of the telemetry controls should be checked to see whether the pre-set positions are set from the central controller or locally from the telemetry receiver.

Iris Control of Lens
Manual Iris
With this type of lens, the iris opening is set manually by rotating a knurled ring on the lens body. Typically, it will have a range of settings from the maximum to fully closed, although the adjustment will be rather coarse. This type of lens is only suitable for indoor applications where the light levels remain fairly constant. It can also be used indoors with cameras having electronic shutters making a significant cost saving. Care must be exercised in using this camera/lens combination in external applications because the camera may not have adequate control to cover the total light range. In addition, manual iris lenses do not usually have a neutral density spot filter to cope with extremely bright sunlight.
In many indoor situations, the general level of light will vary significantly between summer and winter due to light from windows, skylights, etc. Therefore, it is often necessary to adjust the aperture two or three times a year to maintain optimum clarity of the picture.
Automatic Iris
Due to ongoing development, tubed cameras were becoming more sensitive and their use was spreading to more outdoor applications. They were very limited in the range of light that could be coped with. To overcome this problem manual iris lenses were fitted with motors bolted on to the barrel to drive the iris ring. The motors were connected by way of an amplifier to the video output of the camera. This was monitored to adjust the iris ring according to the voltage of the video signal. The lower the voltage then the more the iris would be opened until the correct video voltage was achieved, and the reverse when the video voltage increased. The early amplifiers suffered from the problem of being too sensitive and responding too quickly to changes in the video signal. This caused ‘hunting’ of the iris opening control and resulted in fluctuating contrast of the picture. To overcome this a delay circuit was introduced in the amplifier but this sometimes caused the reverse problem of the picture changing too slowly.
Modern automatic iris lenses are now completely self-contained units produced by the lens manufacturer and containing very sophisticated electronics and microscopic motors. There are three main types of automatic iris lenses.
Iris Amplifier
This type of lens is sometimes referred to as a servo lens. The most common type contains an amplifier and is connected to the video signal of the camera. It is driven by a dc voltage also provided from the camera. It was mentioned in Chapter 3, that the voltage of the video signal is proportional to the amount of light on the imaging device. The video level falls in proportion to the light level. The amplifier is continuously monitoring this voltage to maintain it at 1-volt peak to peak. As the voltage changes so the iris amplifier opens or closes the iris to maintain a constant 1-volt.
Most cameras that provide an automatic iris drive include a socket on the rear. There are three connections, +v, 0v, video. Unfortunately, there is no current standard for this connector but most cameras are packed with the appropriate plug. This can create problems if one camera is substituted for another make during maintenance or service. It can mean that the service engineer has to change the iris plug on site, which is not an easy job. In recognition of this problem, many cameras are now being produced with screw terminals on the rear.
Sensor Lens
This lens includes a light sensor similar to that in a photographic camera. This measures the light levels and adjusts the iris aperture accordingly. It requires a 12-volt dc supply that may be obtained from any source. This type of lens is not very common now having been introduced for use on Vidicon cameras that did not have a video and 12 volt output. The problem was that the light sensor was pre-set and not responsive to the video level, therefore the correct level was always maintained. The vast majority of cameras now provide an automatic lens connection therefore there will only be rare cases where this lens will be required.
Galvanometric Lens
These are also known as a galvometric or galvano lens. This type of automatic iris lens is driven by a reference voltage produced by an amplifier in the camera. In other words, the amplifier is within the camera instead of being part of the lens. The lens contains a driving motor to open and close the lens and a damping coil to prevent hunting. These lenses have four connections, +ve drive, -ve drive, +ve damping, and -ve damping. The camera specification should be checked to ensure that it contains the circuitry for this type of lens. Galvanometric lenses are usually less expensive than lenses with a built-in amplifier. They are simpler to install but can only be used with a limited range of cameras. Again, for this type of lens many cameras are being produced with screw connectors instead of a socket for the lens connection.

Lens Parameters
Focal Length

Diagram 2. Focal Length of Lenses

The rays from infinitely distant objects are condensed by the lens at a common point on the optical axis. The point where the image sensor of the camera is to be placed is called the focal point. A lens has two focal points, the primary principal point and the secondary principal point. The distance between the secondary principal point and the plane of the image sensor is the focal length of the lens.

Diagram 3. Angle of View

Angle of View of Lenses
This is the angle that the two lines from the secondary principal point make with the edges of the image sensor. The focal length of a lens is fixed whatever the size of the image sensor. The angle of view however varies according the size of the sensor.

The angle of view is given by the following formula:

Diagram 4 Angles of View for Different Sensor Sizes

Diagram 5 Focal Lengths for Different Sensor Sizes

The angle of view for a given focal length lens varies according to the sensor size. This is shown in diagram 4. The corollary of this is that for a given view the required focal length varies according to the sensor size as shown in diagram 4.6. This illustrates that for the same field of view, the smaller the format the shorter is the required focal length.
Field Of View

Diagram 6. Field Of View

The field of view is the ratio of the sensor size to the focal length and the distance to the subject. This is shown in diagram 4.7. The ‘width to height’ ratio of the sensor is 4:3. The horizontal and vertical angles and therefore fields of view are different and must be considered separately.

Sensor Sizes

Diagram 7. Sensor Dimensions

Diagram 7.shows the sensor sizes to be used when calculating fields of view and angles of view.For example, if it were required to view a subject 2.5 M high at a distance of 10M using a 2/3” camera and lens the calculation would be as below.
The nearest standard lens in this case would be a 25mm and the actual height of the subject scene would be 2.64 M. The slightly shorter focal length lens provides a slightly wider angle of view.

Most lens brochures give the horizontal and vertical angles of view. The relevant views can be calculated from the formula as follows:
Where: H is the height of the scene, d is the distance from the camera to the scene. This would give the vertical height of the scene using the vertical angle of view. Similarly, the horizontal width of the scene would be calculated from the horizontal angle of view.
Relationship Between Sensor Size and Lens Size
It can be very confusing to establish the actual field of view that will be obtained from a combination of sensor size and lens specification. Lenses are specified as designed for a particular sensor size. A lens designed for one sensor size may be used on a smaller size but not the reverse. The reason is that the extremities of the scene will be outside the area of the sensor. Many people in the CCTV industry have grown up with the 2/3” camera as the most popular and are familiar with the fields of view produced. However the 1/2” and 1/3” cameras are now being extensively used and therefore there are important factors that must be taken account.

Diagram 8. Effect of Sensor Size on View

Diagram 9. Using a Correctly Matched Camera and Lens Format

Diagram 8. shows the effect of using one lens on two different sizes of sensor. The result of using a larger lens format on a smaller lens format is to create the effect of a longer focal length, which is a narrower angle of view.
Diagram 9. shows the result of using a lens designed for a 1/2” format on a 1/2” sensor. This is an important consideration when deciding the most appropriate lens for a required field of view. The design size of the lens must be related to the size of the sensor being used.
To summarise then:
1. A lens designed for one format may be used on a smaller format camera but will produce a narrower angle of view.
2. A lens designed for one format may not be used on a larger format camera.
3. Assuming a focal length has been assessed based on a particular format of camera and lens, and it is then decided to use a smaller format camera, the same field of view will only be obtained if a shorter focal length lens is used.
4. Always check the angle of view for the particular lens and camera combination it is intended to use.
5. Charts at the end of this chapter provide guidance on the selection of lenses and the relationship between different formats of camera and lenses.

Aperture
The size of the aperture is called the ‘f number’ of the lens, e.g. f1.4, f1.2, etc. This is a mechanical ratio of the lens components and is specified as:
The effective diameter is related to the size of the front lens. Note that this is effective diameter and not the actual diameter. This is a measure of the amount of light that the lens will pass to the imaging device. As stated it is a ratio and does not refer to the quality of the lens. The smaller the number then the larger is the aperture. The figure given in specifications for lenses is the maximum aperture and this value is often followed by the minimum aperture. For instance, f1.4 -- f360, this second value being important if the camera is very sensitive such as an intensified sensor. Intensified cameras often require a minimum aperture as small as f1500. From the formula above it may be calculated that with a 16mm lens having the aperture set to f360 the effective diameter will be only 0.04mm. Even so, this could allow too much light to the sensor of an intensified camera and damage the tube or flare out the picture.

Having said that the f-number is a ratio, this does not imply that a lens with a lower number is better than one with a higher number. There are other factors that affect the light transmission through a lens. However, when comparing the major brands of lenses it is sufficient to use the f-number unless the application is especially demanding, where, for instance, image comparison or ultra fine resolution is necessary.

The efficiency of a lens and the amount of light it can transmit depend on many factors that lens designers must consider. However, ultimately a lens must be a commercial proposition and affordable to the CCTV installer and the customer. Two factors that affect the cost of a lens are the size of the glass elements and the number of elements. Therefore, it is less expensive to produce a 16mm f1.8 lens than it is to produce a 16mm f1.2. Consequently, some manufacturers produce the same focal length lens in two variations of f-number. For indoor conditions with ample light, or outdoor use in daylight only, the cheaper f 1.8 lens would be satisfactory and could represent a saving in cost. Exercise care in selecting the cheaper lens if the application is outdoors with low light conditions. As can be seen from this chapter, this would require nearly three times as much light as the f1.2 lens.

How aperture numbers are calculated
The scale of ‘f’ numbers, 1.4, 2.0, 2.8, 4, 5.6, etc. is such that successive numbers halve the amount of light passed to the sensor. These particular numbers are known as "full stops". This only applies to "full stops"; there are also half stops, which are numbers half way between full stops, and one-third stops In other words, the amount of light is proportional to the cross sectional area of the light rays entering the lens.

It can be shown that the f number,

From this equation the following can be derived;

If the illuminance is defined as ‘E’ lux, the equation can be shortened to;
If reflectance (R) is taken into account, this now becomes,
Another consideration is, how efficient is the lens at passing the maximum amount of light. There are several factors that determine the efficiency of a lens and of course they all cost money. When light passes through a glass/air boundary some is lost through reflection and refraction; this is reduced in the more expensive lenses. In addition, different light frequencies are refracted at different angles; special coatings are used to ensure that all frequencies are transmitted in parallel rays. The factor that measures the efficiency of a lens is known as the transparency ratio, (t) from which is calculated the transmission ratio (T).
The transparency ratio (t) is a function of the lens design and the number of glass elements. This is generally only available from the manufacturer. The transmission ratio (T) is the effective lens stop after adjusting for the transparency ratio (t) and is defined by

The resulting number will always be larger than the specified f-number.

For example, an f-1.4 lens having a transparency ratio (t) of 0.785 would have an effective aperture of f 1.58. This would be the value to use when calculating the light transmitted through a lens rather than the published f-number. All reputable manufacturers should be able to provide information on the transmission ratios for their lenses.
If this is now taken into account, the relationship becomes.

If an example is now worked using;
Transparancy ratio, t=0.785,
Reflectance, R=0.89,
Scene illumination, Escene=15 lux, Lens aperture, f=1.4,
Then, the light required on the sensor

The effect of sensor size
here is yet another factor that affects the efficiency of a camera/lens combination.

As stated in a previous article, light is energy measured in Watts per square Metre. Therefore, if the area of a sensor is known then the resultant power in watts can be calculated. The nominal areas of the sensors in common use are listed in table 2.

Table 2, areas of sensors

The power produced by each individual pixel in the sensor is directly proportional to its area. If three cameras are considered each with the same resolution of say 500 lines then the number of pixels on each sensor must be the same. The result of this is that the pixels on each smaller size of sensor must also be smaller. Therefore, the power produced will be less for the same aperture setting, i.e. the same amount of light energy. It is assumed that the light energy to produce a full 1-volt pp video signal is 5.0 mW/M2
If for the sake of an example, a light source of 1,000 milliwatts per square Metre is passed to the sensor via an f-1.8 aperture lens. The amount of light passed by the lens will be 7.5% = 75 mW/M2. From this, the power output can be calculated for each sensor. This will be the power multiplied by the area of the sensor. The result is shown in table 3.

Table 3-power output of sensors

Therefore the 1/2" and 2/3" sensors will be producing insufficient power for a full video signal. The answer is to use a lens with a larger aperture for these sensors so that more energy is passed to maintain the output power. This is summarised in table 4

Table 4-power output corrected by lens f-stop

This is the reason that many 1/3" cameras have the sensitivity specified with an f-1.0 or sometimes an f 0.9 aperture. Beware though, there are only a limited number of lenses made to the 1/3" format. If the longer focal length lenses must be used they usually have smaller apertures (higher f-numbers) and pass less light energy.
The contra to this argument is that if a sensor of one size has the same size pixels as a larger one, then the light required will be the same. However the total number of pixels will be fewer and the resulting resolution will be proportionally less. There is no such thing as a free lunch!