| AC | | | | BRIDGING SWITCHER |
| Alternating Current | | | | Term for a multi-input sequential video switcher, |
| ACCESS CONTROL SYSTEM | | | | which includes a sequencing output and spot |
| Electronic system used to allow, restrict and track | | | | output. |
| the movement of people through entry/exit | | | | BRIGHTNESS |
| points in a site. This is achieved through the use | | | | Term for the intensity of illumination of a |
| of electronic individual codes, keys or cards etc, | | | | reproduced video picture. |
| to release a locking mechanism. | | | | BRIGHTNESS CONTROL |
| ACTIVITY DETECTION | | | | Control, which increases or decreases the |
| A feature built into some multiplexers, which is | | | | illumination of phosphors on a monitor screen to |
| used to detect movement within a camera's field | | | | vary the brightness. |
| of view that is then used to improve camera | | | | BRAID |
| recording update rate. | | | | A group of textile or metallic filaments |
| AGC (AUTOMATIC GAIN CONTROL) | | | | inter-woven to form a tubular structure, which |
| An electronic circuit that is used to boost the | | | | may be applied over one or more wires, or |
| video signal in a camera in low light conditions. Use | | | | flattened to form a strap. |
| of this feature will usually give a "noisy" or grainy | | | | BYTE |
| picture. When comparing camera specifications | | | | A group of eight bits. |
| always use data with AGC off. | | | | BROADCAST CAMERA |
| ALARM INTERFACE | | | | High quality, high-resolution camera used by the |
| A facility which allows the use of external alarm | | | | professional broadcast industry. |
| equipment such as PIR's, magnetic contacts etc | | | | CAD |
| to be connected to CCTV equipment so that | | | | Computer Aided Design. Method of producing |
| when the alarm is activated the CCTV equipment | | | | complex designs using computer based software |
| will automatically carry out a pre programmed | | | | programs. |
| function such as switching to record a given | | | | CABLE COMPENSATED AMPLIFIER |
| camera. | | | | High frequency signals are attenuated when |
| ALC (AUTOMATIC LIGHT CONTROL) | | | | transmitted through cables. A Cable Compensated |
| A feature of an Auto Iris lens used to adjust the | | | | Amplifier boosts the high frequency signals |
| between peak and average voltage which will | | | | depending on the cable distance. This ensures the |
| emphasise detail in bright areas (peak), or | | | | minimum video loss. |
| shadows (average). | | | | CABLE CORE |
| ALGORITHMS | | | | The central part of the cable, which actually |
| Complex mathematical formulae or rules used to | | | | carries the video, power and control signals. This |
| solve complex problems in CCTV they are used | | | | can be constructed as a single conductor, or from |
| to achieve digital compression of a video picture. | | | | wire strands. |
| ALIASING | | | | CABLE JACKET |
| Also known as Moiré patterning. This is an | | | | The outer protective coating, which covers the |
| effect that occurs when an analogue signal is | | | | Cable Core. |
| sampled digitally at a sampling frequency less than | | | | CCIR |
| twice the signal frequency. The effect can be | | | | Commitee Consultatif International des |
| minimised by a technique known as optical | | | | Radiocommunique. European standardisation body |
| low-pass filtering. | | | | that has set the standards for television signals in |
| ANALOGUE SIGNAL | | | | Europe. 625 lines, 25 frames per second. |
| A signal in which the level is represented by a | | | | CCTV |
| directly proportional voltage. In video the cameras | | | | Closed Circuit Television. Television system |
| scene is represented by varying the voltage in | | | | intended to be viewed by restricted personnel and |
| the video signal where the voltage is directly | | | | with a dedicated purpose. Pictures from a CCTV |
| proportional to the light level. | | | | system are not intended to be broadcast for |
| ALKALINE BATTERY | | | | general viewing. |
| DC power source with a longer life than a | | | | CCVE |
| standard battery. Cannot be recharged. | | | | Closed Circuit Video Equipment. Alternative term |
| AMPLITUDE | | | | for CCTV. |
| Expression of the strength of a video signal at a | | | | CFA |
| given point. Measured in Volts. | | | | Colour Filter Array. Optical pixel filters used in |
| ANGLE OF VIEW | | | | single chip colour CCD cameras, to produce the |
| Represents the area of a scene (maximum | | | | colour components of a video signal. |
| horizontal and vertical angle) that can be seen | | | | CHANNEL SEPARATION |
| through a lens. Measured in degrees. | | | | The term for the separation of signals when |
| APERTURE | | | | multiplexed at different frequencies for |
| The light gathering part of a lens. The size of the | | | | transmission down a single cable. |
| aperture is controlled by the Iris. Aperture size is | | | | CHROMATIC ABERRATION |
| expressed as an "f" number. The lower the "f" | | | | Optical term, which refers to the distortion of an |
| number the greater the amount of light gathered | | | | image as a result of a scattered focal point |
| by the lens. | | | | caused by a defect in a lens. A combination of |
| ASPECT RATIO | | | | lens can be used to correct this effect. |
| The ratio between the width and height of a | | | | CHROMINANCE SIGNAL |
| video picture. The standard Aspect Ratio for | | | | The part of the video signal that contains the |
| CCTV Monitors, NTSC and PAL systems is 4:3. | | | | colour information. In composite video The |
| ASPHERICAL LENS | | | | chrominance signal is multiplexed at a higher |
| A type of lens, which has a non-spherical shape. It | | | | frequency than the signal and transmitted down |
| is harder and more expensive to manufacture, | | | | the same cable. In S-VHS this signal is transmitted |
| but it offers certain advantages over a normal | | | | along a separate cable. |
| spherical lens. | | | | CLADDING |
| ATTENUATION | | | | The outer part of a fibre optics cable. The |
| The decrease in magnitude of a signal, as it | | | | cladding is less dense than the central core, and |
| travels through a medium. Used to describe signal | | | | acts as an optical barrier to prevent the |
| loss in a transmission system. Measured in decibels | | | | transmitted signal from leaking away from the |
| (dB). | | | | core. |
| AUDIBLE DETECTOR | | | | C-MOUNT |
| A device used to detect sound. In CCTV system | | | | Standard lens mounting with a 17.526mm back |
| it can be interfaced with a switcher to switch on | | | | flange (distance between the lens mount and the |
| a nominated camera when the detector is | | | | focal point). Normally used on 2/3" and 1" cameras |
| activated. | | | | and lenses. |
| AUTO BALANCE | | | | COAXIAL CABLE |
| System used in colour cameras to detect and | | | | Term for cable in which two or more conductors |
| automatically correct errors in the amplitude of | | | | share the same axis. Normally consists of a single |
| colour signals. | | | | inner core and an outer shield. This is the standard |
| AUTO IRIS (AI) | | | | cable used to carry video signals in CCTV |
| An automatic method of varying the size of a | | | | installations, because it does not produce and is |
| lens aperture to allow the correct amount of light | | | | not influenced by external fields. |
| to fall on the imaging device. The lens Includes a | | | | COLOUR STRIPE FILTER |
| tiny motor and amplifier, which are used to | | | | A filter that is placed in front of a colour CCD chip |
| maintain a one-volt Peak to peak video signal. | | | | to break up the light into the basic colours (Red, |
| AUTO PAN | | | | Green, and Blue) The individual colours are then |
| A feature of a pan and tilt head or dome, which | | | | directed at different pixels on the chip. |
| allows the camera to pan continually between two | | | | COMMON SYNC |
| preset points. | | | | Device used to synchronise cameras by |
| AVERAGE VIDEO SIGNAL | | | | generating a synchronising pulse that is sent to all |
| Represents the average light level of a picture | | | | cameras connected to it. |
| and is used to open or the iris in an Auto Iris lens. | | | | COMPOSITE VIDEO |
| BACK-FOCUS | | | | The complete video signal, comprising both the |
| A fine mechanical adjustment in a camera that is | | | | video and sync information. |
| used to adjust the imaging device relative to the | | | | CONCAVE LENS |
| lens to ensure that it is at the exact focal point | | | | Type of lens in which the light rays passing |
| for the lens fitted. This adjustment is especially | | | | through it are made to diverge by the inward |
| important when fitting a zoom lens. | | | | curve of the glass surface. |
| BACKLASH | | | | CONDUIT |
| An effect noticed in Pan and Tilt units, whereby | | | | Plastic or metallic pipe, which is used to conceal |
| the unit does not come to a smooth stop at the | | | | and protect cables and wiring. |
| end of the pan movement. This is usually caused | | | | CONTRAST |
| by play in the mechanical components of the unit | | | | The difference in intensity between the darkest |
| or by attempting to bring the unit to an instant | | | | and the brightest parts of an image. |
| stop. | | | | CONTRAST CONTROL |
| BALANCED SIGNAL | | | | The control on a monitor used to change the |
| This is a video signal that has been converted to | | | | contrast by varying the amplitude of the video |
| enable it to be transmitted along 'twisted pair' | | | | signal. |
| cables. Usually used where the signal has to be | | | | CONVEX LENS |
| transmitted over long distances, which would | | | | Type of lens in which the light rays passing |
| produce unacceptably high losses in Coaxial cable. | | | | through it are made to converge by the outward |
| BANDWIDTH | | | | curve of the glass surface. |
| The frequency range required to carry an | | | | COVERT CAMERA |
| electronic signal without attenuation or loss. | | | | Type of CCTV camera, which is concealed to |
| BARREL DISTORTION | | | | allow video recordings to be made without the |
| A distortion in a monitor due to non uniform | | | | knowledge of the subjects. |
| scanning which causes the image to appear to | | | | CPU |
| bulge outward like a barrel. | | | | Central Processing Unit. The heart of a computer |
| BAUD | | | | or computer based device. |
| Data transfer rate, named after Maurice Emile | | | | CRIMPING |
| Baud, Equal to 1bit per second. | | | | Term used to describe the process of joining a |
| BIT | | | | cable to a connector without screwing or |
| Acronym formed from "binary digit". The basic | | | | soldering. Requires a special crimping tool to |
| unit of information in a computer or digital system | | | | ensure a proper connection. |
| Either 1 or 0. | | | | CRO |
| BLACK LEVEL | | | | Cathode Ray Oscilloscope (see Oscilloscope). |
| Part of the video signal, just above the sync level | | | | CROSSTALK |
| corresponding to 0.3v This is where black parts of | | | | Noise generated by the interference between |
| an image are electronically represents. | | | | adjacent video, audio or data signals in a |
| BLANKING PULSE | | | | multiplexed signal. |
| A black pulse added to a monitor signal during the | | | | CS-MOUNT |
| fly back period to make the return trace video | | | | Standard lens mounting with a 12.5mm back |
| signal invisible on the screen. | | | | flange (the distance between the lens mount and |
| BNC | | | | the focal point) Normally used on modern |
| Standard connector used to connect coaxial | | | | ¼", 1/3", and ½" cameras and lenses. |
| cables to CCTV equipment or each other. | | | | |