Glosary

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AC Power	Alternating Current Power. In the United States, the standard AC Power is single-phase 117VAC/60Hz and is provided from power outlets in the house. 24V AC power can be produced from an AC Adapter.
Alarm Sensor	Like Video Motion Detector, detects changes of motion to produce an alarm.
Anti-aliasing	A procedure employed to eliminate or reduce (by smoothing and filtering) the aliasing effects.
Auto-Focus Lens	Automatically adjusts the lens focus from surrounding scene and keeps a moving object in focus.
Automatic Gain Control (AGC)	This is a feature of many CCTV cameras that helps keep the strength of the output signal constant, even when the light level changes. In other words, it boosts the signal strength at low light levels, and caps it at higher levels.
Back Light Compensation (BLC)	This is a feature of cameras that automatically adjusts the image to compensate for bright sunlight or bright lights, to give more detail on the darker areas of the image. For example to focus on the detail of a face of a person that has the sunlight shining from behind.
Brightness Control	The manual bias control on a cathode ray tube or other display device that controls the average brightness and the contrast of a picture.
Camera Sensor	Video image sensor. CCD or C-MOS chip.
CCIR	International Radio Consultative Committee; has made the technical recommendation for the European 625 line standard for video signals.
CCTV	Closed Circuit Television. It does not broadcast TV signals but transmits them over a closed circuit through electrically conducting cable or wireless transmitter and receiver.
CCTV Camera	A unit containing an imaging device that produces a video signal in the baseband form, usually with synchronization pulses and color information (composite video).
Chip	An integrated circuit in which all the components (resistors capacitors and semiconductors) are micro-fabricated on a tiny piece of silicon or specialist material (silicon on sapphire. Often used to refer to the detector in a CCD camera.
C Mount Lens & CS Mount Lensr	CCTV lenses are available in two different lens mounts. "C-mount" lenses have a flange back distance of 17.5mm vs. 12.5mm for "CS-mount" lenses. Many of today's cameras can accept either type of lens, but it is important to make sure that camera and lens.
Composite Video	A combined signal in a television transmission. Standard format such as NTSC, PAL or SECAM. The picture signal, blanking signal, and vertical/horizontal synchronizing signals are all combined.
Compression	Digital video pictures can be compressed with a number of techniques. These include, JPEG, M-JPEG, MPEG and Wavelet.
CRT	Cathode Ray Tube. The vacuum tube part of a monitor or television.
Date/Time Generator	Installed between a CCTV camera and a monitor, it generates the information of Date, Time and camera ID.
DC Power	Direct Current Power; can be derived from an AC adapter or from a battery. Among DC voltages of 6, 9, 12, 24, 28, 12VDC is most common in the CCTV industry.
Decibel (dB)	The power or voltage ratio of two signals.
Direct Drive (DD)	Dynamic Host Configuration Protocol; lets network administrators manage centrally and automate the assignment of IP addresses in an organization's network.
DHCP	Dynamic Host Configuration Protocol; lets network administrators manage centrally and automate the assignment of IP addresses in an organization's network.
DNS	Domain Name System. A general purpose distributed, replicated, data query service. Its principal use is the lookup of host IP addresses based on host names.
DSP	Digital Signal Processing. It usually refers to the electronic circuit section of a camera capable of processing or enhancing signals.
Dwell Time	The length of time a switcher displays one camera before sequencing to the next.
EIA	Electronic Industries Association. American standard for B/W camera system.
Electronic Iris (EI)	This is an electronic implementation of an auto iris. It uses electronics to simulate the effect of opening and closing the iris, by increasing or decreasing the effective shutter time of the camera.
Electronic Shutter(ES)	Compensates for moderate light changes in indoor applications without the use of auto iris lenses.
Ethernet	The most widely installed Local Area Network (LAN) technology. Specified in a standard IEEE802.3.10/100 BASE-T, the most commonly installed Ethernet system, provides transmission speed up to 100 megabits per second.
External Sync.	An external sync allows a piece of equipment to take its video synchronisation from another unit, so that it can align itself with the system as a whole.
Extranet	A private network. It uses the Internet Protocol to securely share part of a business information with suppliers, vendors or others.
Focal Length (FL)	The distance between the optical centre of a lens and the principal convergent focus point.
Format	The size of the cameras imager. Current standards are 1/2, 1/3, 1/4 inches.
Frame	A whole video image; is composed of two interlaced fields. A CCD chip produces 30 frames per second at NTSC system and 25 frames at PAL.
Gamma	Degree of contrast in a video picture between output magnitude and input magnitude.
HAD	Hole Accumulated Diode. A type of CCD sensor with a layer designed to accumulate holes (in the electronic sense), thus reducing noise level.
HDCP	High-Bandwidth Digital Content Protection. HDCP encryption is used with high-resolution signals over DVI and HDMI connections to prevent unauthorized duplication of copyrighted material.
HUB	As a network product, a hub may include a group of modem cards for dial-in users, a gateway card for connections to a Local Area Network (LAN), and a connection to a line.
ICMP	Internet Control Message Protocol. A message control and error-reporting protocol.
Image Device	The detector in the camera, either a tube or CCD solid state device.
Image size	Reference to the size of an image formed by the lens onto the camera pickup device. The current standards are: 1", 2/3", 1/2" and 1/3" measured diagonally.
Interlace	PAL video signals transmit odd and even lines alternately. This is a 2:1 interlace. The two sets of lines are combined to form each single frame.
Internal Sync.	Devices with internal sync, have an internal crystal to provide sync pulses, without needing reference from any external device.
Infra Red (IR)	Low frequency light below the visible spectrum. This is often used for covert or semi-covert surveillance to provide a light source for cameras to record images in dark or zero light conditions.
ISDN	Integrated Service Digital Network. A set of standard for digital transmission over ordinary telephone copper wire.
JPEG	JPEG is a standard for coding/compression of still pictures. It is used in the CCTV systems to compress and store individual frames of video.
Lens	An optical device for focusing a desired scene onto the imaging device in a CCTV camera.
Line Lock	In CCTV, this usually refers to multiple cameras being powered by a common alternative current (AC) source (either 24 V AC, 110 V AC or 240 V AC) and consequently have field frequencies locked to the same AC source frequency (50 Hz in CCIR systems and 60 Hz in EIA systems).
Loop	This refers to connecting an additional device in parallel with an existing video cable. For example, when driving a video recorder as well as a monitor from the same video signal.