Glossary

Aberration

Is a term from optics that refers to anything affecting the quality of the image in regards to the original scene.

Absorption

Parts of a video signal are absorbed by the material, e.g. by a fibre cable. Therefore the transmission distance is not infinite.

AC

Alternating current. - Mains power is alternating current. Current voltages are 24 V AC, 115 V AC or 230 V AC.

Activity Detection

Is a feature built into equipment for detecting movement within the camera field of view, which is then used to improve the cameras recording update rate.

ADC

Analogue to digital conversion is usually the first stage of an elec- tronic device that processes signals into a digital format. The signal can be video, audio, control output or similar.

AES

Automatic electronic shutter - See “Shutter”.

AGC

Automatic Gain Control is the electronic circuitry in a camera that is used to increase the video signal and becomes operational when the light level is low. This usually introduces 'noise' in the picture giving a grainy appearance.

AI

Automatic iris - See “Auto iris”.

Alarm Input

Is a equipment connection, which allows external alarms like PIRs, reed switches, etc to be connected to CCTV equipment so that a nominated camera is switched on when an alarm input signal is received by the received.

ALC

Automatic Light Compensation is a setting in an auto iris lens to con- trol the iris opening. It can be adjusted between peak and average to respond to the bright part of the scene (peak setting) or the average value of the video signal (average setting).

Algorithms

Are complex mathematical formulae or rules used to solve problems. In CCTV, they are used to achieve digital compression of a video picture.

Ampere

Unit symbol A. Is the unit to measure electric currents.

Amplitude

The amplitude refers to the level of the video signal at a point and is measured in volts.

Analogue Signal

In video, the analogue signal represents the camera scene in the form of varying voltage levels in the video signal, the voltage being directly proportional to the light level.

Angle of Refraction

The angle of refraction is the deflection of light when it travels from one medium into another.

Angle of View

Represents the area of the scene (maximum horizontal and vertical angle) that can be seen through a lens. It is measured in degrees.

Aperture

The lens aperture dictates the amount of light reaching the surface of the CCD. The size of the aperture is controlled by the iris adjust- ment, by increasing the f-stop number (F1.4, F1.8 etc) less light is passed by the lens to the CCD.

Archive

The term archive is used for long term off line storage. In digital sys- tems, pictures are generally archived onto some form of hard disk.

ASCII

This is an internationally acknowledged character set standard.

Aspect Ratio

This is the ratio between the horizontal and the vertical lengths of the image. The aspect ratio for NTSC and PAL systems is 4:3, which means 4 horizontal units by 3 vertical units.

Aspherical Lens

Using an aspherical surface these types of lenses are more difficult and more expensive to manufacturer. They are, however, fewer lens aberrations to correct for with an aspherical lens.

Asynchronous data transmission

Stands for a transmission technique that uses control bits in the video line to ensure correct transmission.

Attenuation

The decrease or loss in magnitude of a wave, or a signal, as it travels through a medium or an electrical system. Attenuation is measured in decibels (dB).

Auto Balance

Is a system of detecting and automatically correcting errors in the amplitude of colour signals.

Auto Iris (AI)

A lens with an auto iris can automatically adjust to correct the amount of light that is passed to CCD of a camera. There is a tiny motor and amplifier built into the lens body, which receives a control signal from the camera to maintain a constant one volt peak to peak video level. There are two manual controls on the lens to compen- sate for varying conditions of 'peak' and 'average' light.

Auto pan

Is a feature of a pan tilt or pan only head which allows the head to continuously move (pan) left and right between two fixed points. These fixed points can be set by adjusting the limit switches in the head.

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© Siemens Building Technologies Group

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Siemens CRT, TFT manual Glossary

CRT, TFT specifications

Siemens, a prominent name in electronics and engineering, has made significant contributions to display technology, particularly in the realms of Thin Film Transistor (TFT) and Cathode Ray Tube (CRT) displays. These technologies have paved the way for advancements in visual media, ranging from television sets to computer monitors.

TFT display technology, a type of LCD (Liquid Crystal Display), employs thin film transistors to produce brighter and more vibrant images. One of the main features of TFT displays is their ability to deliver high resolution and excellent color reproduction, making them ideal for various applications such as smartphones, tablets, and laptops. TFT screens utilize an active matrix approach, which allows each pixel to be controlled individually. This method results in faster response times and improved image quality, with less motion blur, compared to older passive matrix displays.

One of the key characteristics of TFT technology is its versatility in different settings. It supports a wide range of viewing angles, which enhances the user experience whether one is viewing the display head-on or at an angle. Additionally, TFT displays are known for their thin profile and lightweight design, contributing to the overall portability of devices that incorporate them.

On the other hand, CRT technology, which was once the standard for televisions and computer monitors, uses electron beams and phosphorescent screens to produce images. One of the defining features of CRTs is their ability to display deep blacks and a wide color gamut. CRT technology can achieve high refresh rates, reducing flicker and improving the quality of fast-paced visuals. However, CRTs tend to be bulkier and heavier than modern display technologies like TFT.

Despite the evolution towards flat-panel displays, CRT technology is still appreciated for its natural color and motion portrayal. Siemens has leveraged these characteristics to produce quality CRT monitors that were favored in professional settings, including graphic design and medical imaging, where color accuracy is paramount.

In summary, Siemens has played a vital role in advancing both TFT and CRT technologies. TFT displays are recognized for their high resolution, fast response times, and design versatility, while CRTs are celebrated for their rich color and depth. As technology continues to advance, the legacy of these display types remains influential in shaping modern electronic devices.