Glossary U-Z

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UHF signal - Ultra high frequency signal.

In television it is defined to belong in the radio spectrum between 470 MHz and 850 MHz.

Unbalanced signal

In CCTV, this refers to a type of video signal transmission through a coaxial cable. It is called unbalanced because the signal travels through the center core only, while the cable shield is used for equating the two voltage potentials between the coaxial cable ends.

Uninterrupted Power Supply (Ups)

Equipment that supplies power to a system in the event the primary power is lost. It may consist of batteries or auxiliary motor generators.

Unterminated (Hi-Z)

Video input of a piece of CCTV equipment, wired so as to allow the video signal to be fed to further equipment. Does not necessarily include extra sockets for the extra coaxial cables.


Variable bit rate

Operation where the bit rate varies with time during the decoding of a compressed bit stream.

Varifocal Lens

See Zoom Lens. Usually not motorized (manual).

Velocity of propagation

Speed of signal transmission. In free space, electromagnetic waves travel at the speed of light. In coaxial cables, this speed is reduced by the dielectric material. Commonly expressed as percentage of the speed in free space.


A device that records video images on tape.

Vertical interval

The portion of the video signal that occurs between the end of one field and the beginning of the next.

Vertical Interval Switching

Sequential switchers waiting until the current field has finished before they display the next camera, even though the dwell time has elapsed.


A multiplexer feature that uses a pulse generated by the VCR so that the multiplexer automatically adjusts to the VCR time lapse speed.

VHF - Very high frequency

A signal encompassing frequencies between 30 and 300 MHz. In television, VHF band I uses frequencies between 45 MHz and 67 MHz, and between 180 MHz and 215 MHz for Band III. Band II is reserved for FM radio from 88 MHz to 108 MHz.

Video bandwidth

The highest signal frequency that a specific video signal can reach. The higher the video bandwidth, the better the quality of the picture.

Video Motion Detection (V.M.D.)

A system that uses the video signal from a camera to determine if there is any movement in the picture and set of an alarm. By using Cameras and(or) software, it is possible to identify movement in a very small group of pixels. When motion is detected several options can occur. A DVR can start recording, an alarm can sounded, lights can be turned on or even a pre-recorded announcement can be played over a PA system.

Video Type Lens

An auto-iris lens without an internal circuit to control the iris. All iris control voltages come from a circuit located within the camera.

VLF - Very low frequency

Refers to the frequencies in the band between 10 and 30 kHz.


WAN - Wide area network

A computer network serving a large area. Typically a town, city, state or larger.

White Light

The entire spectrum of visible light.


Windows Media Audio. An audio compression format similar to MP3, but with digital rights management (copy protection and usage restrictions) built-in by Microsoft.




A video format found in Super-VHS video recorders. Luminance is marked with Y and is produced separate to the C, which stands for chrominance. Thus, an S-VHS output Y/C requires two coaxial cables for a perfect output.

Y, R-Y, B-Y

The general set of component video signals used in the PAL system as well as for some encoder and most decoder applications in NTSC systems; Y is the luminance signal, R-Y is the first color difference signal and B-Y is the second color difference signal.

Y, U, V

Luminance and color difference components for PAL systems; Y, B-Y, R-Y with new names; the derivation from RGB is identical.


Zero Lux

Refers to video imaging in pitch black (0.0 lux) lighting conditions. Monochrome CCD cameras can use IR infra red lighting to yield crisp and distinguishable video images when absolutely no visible light is available.


The ability to change the magnification of a scene.

Zoom Lens

A lens with a variable focal length. This lens may be effectively used as a wide angle, standard, or telephoto lens by varying the focal length of the lens. A varifocal lens.

Zoom Ratio

The ratio of starting focal length (wide position) to the ending focal length (telephoto position) of a zoom lens. Typically 10X.


One or more rooms powered by one or more amplifiers, which are all fed by one source. A home can be divided into multiple zones, which can play multiple sources, even though several rooms (say, the kitchen, dining room, and living room) all play the same source.

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