CCTV Glossary

A   B   C   D   E   F   G   H   I   L   M   N   P   Q   R   S   T   V   Z

A

Alarming -- Feature on some CCTV equipment which allows the equipment to provide a simple switch closure (usually) in response to a designated input alarm signal.

Aperture Opening (Lens) -- Controls the amount of light reaching the surface of the camera pick-up device. Aperture size is controlled by the iris. Increasing the f-stop decreases the amount of light reaching the pick-up device.

Aspect Ratio -- Ratio of picture height to picture width. Standard ratio is 4:3.

Automatic Brightness Control -- Electronic circuitry which automatically controls the brightness of video monitors in relation to ambient light.

Automatic Frequency Control (AFC) -- Circuitry that automatically maintains the desired frequency.

Automatic Gain Control (AGC) -- Circuitry that automatically adjust the signal to proper strength.

Automatic Light Control -- Process by which the brightness upon the camera pick-up device is automatically adjusted according to the brightness of the scene.

Auto Pan -- Automatic back and forth camera motion

Auto Scan -- Same as Auto Pan

Auto Iris Lens -- Camera lens which automatically adjust for proper light levels

Attenuation -- A decrease in signal strength.

B

Bandpass -- Specific range of frequencies allowed to pass through a device

Bandpass Filter -- Filter that passes only a specific band of frequencies

Bandwidth -- Range of frequencies in which a specific device will properly opera

Blooming -- Defocusing effect that occurs around bright areas of a picture when an increase in brightness occurs.

BNC -- Most commonly used video cable connector.

Bridging -- When a high impedance video line is paralleled, usually through a switch, to a source of video.

C

C-Mount -- Former industrial standard lens mounting format

Candlepower -- Unit measure of incident light

CCD (Charged Coupled Device) -- The "chip" in a solid state camera that replaced the camera tube .

CCTV -- Closed Circuit Television

Coaxial Cable -- Cable commonly used to transmit video signals. It consists of a metallic shield with one or more center conductors which are isolated from each other and the shield.

Composite Video -- Video signal that contains the picture signal, and vertical and horizontal blanking and sync pulses.

Compression -- Reduction in gain at one level of a video signal with respect to the gain at another level of the same signal

Contrast -- The range of light and dark values in a picture or the ratio of maximum and minimum brightness.

Crosstalk -- Undesired signal that interferes with a desired signal

CS Mount -- New standard lens mounting format

D

dB (decibel) -- The power ratio of two signals.

Depth of Field -- Front to back area in the camera view which is in focus. The better the lighting, the greater the Depth of Field possible.

Duplex (Multiplexer) -- A multiplexer which allows viewing of multiple "pictures" during recording

Dwell  -- Length of time a video switcher holds a camera's "picture" before switching to the next camera's "picture"

Distribution Amplifier -- Device used to send a single video input signal to multiple video output devices

E

EIA -- US standard, 525 TV lines and 60 fields

F

f-Number -- Indicates the brightness of the image formed by the lens and controlled by the iris. A smaller f-number means a brighter image.

f-Stop -- Indicates the speed of a lens. The smaller the number, the greater the amount of light that passes through the lens, thus allowing for better low light camera performance.

Fiber Optics -- Flexible glass fibers used to conduct signals.

Field -- One of the two equal parts into which a TV frame is divided.

Field Frequency -- Number of fields transmitted per second in a TV system. The NTSC standard is 60.

Field of View -- The horizontal or vertical picture size at a given distance from a camera to the subject.

Focal Length -- The distance from the centerline of the lens to the camera pick-up device. It determines the size of the image and the angle of the field of view as seen by the camera through the lens.

Foot Candle (FC) -- Unit of measurement of the intensity of light. 1 FC = 10 lux

Frame -- One complete TV picture.

G

Gain -- The amplification a system provides to a signal.

Gen-Lock -- Method used to synchronize one or more cameras by external means. Typical methods are composite video, composite sync, and horizontal or vertical sync.

Ground -- Electrical point that is common to either metal chassis, a terminal, or a ground bus.

H

Homing -- Process of displaying a given camera output on a given monitor

Horizontal Blanking -- Electrical signal produced at the end of each scanning line

Hum -- Electrical disturbance at the power supply frequency or harmonic.

I

Infra Red (I.R) -- Frequency of light, invisible to the human eye, used for covert surveillance and low light camera use.

Image Intensifier -- Electronic device used to provide a brighter output image than the input image.

Impedance -- Opposition to the flow of electrical current.

Incident Light -- Amount of light directly over an object.

Insertion Loss -- Signal strength lost due to the insertion of a piece of equipment in the line.

L

Looping -- Term used when a high impedance device is connected in parallel to a video source.

Lux -- Unit of measurement of the intensity of light. 10 lux = 1 FC

M

Matrix Switcher -- Normally used in larger camera systems, this switcher allows any of the systems cameras to be routed to any of the systems monitors.

Modulate -- To vary the amplitude or frequency of a signal

Monochrome -- Having one color. In CCTV it is Black and White.

Multiplexer -- Device which allows the recording/playback of multiple cameras on a single time lapse recorder with little loss of information.

N

Noise -- Random electrical energy or interference

NTSC -- National Television Systems Committee. Formulated the standards with the FCC for color television in the U.S.

P

Pan -- Horizontal camera movement

Passive -- Non powered element of a system

Peak-to-Peak -- Amplitude difference between the most positive and negative points of a signal

Pinhole lens -- Lens with a very small front, easily concealed, for use in covert applications.

Q

Quad -- Device that simultaneously places the pictures from four cameras onto one video monitor

R

Resolution -- Measure of the ability of a CCTV system, or one of it’s components, to produce detail.

Roll -- Result of the loss of vertical sync which causes the picture on a monitor to move up or down

S

Saturation (color) -- The vividness of a color which is directly related to the amplitude of the chrominance signal.

Scanning -- Horizontal (panning) camera motion

Sensitivity (pickup device) -- The amount of light needed for the pickup device to operate

Signal to Noise Ratio -- Ratio between a useful signal and unwanted noise

Spot Filter -- A small device used to increase the f-stop range of a lens.

SVHS -- High resolution video recording format.

SYNC -- Electronic pulses inserted in a video signal for assembling picture information in the proper position.

T

Time Lapse VCR -- VCR that can record for extended periods of time on a single video tape by using frequent tape "pausing". The longer the time of recording, the fewer number of "pictures" recorded per second. 

V

Vari-focal Lens -- Lens with an adjustable focal length, such as 3.5-8mm, 2.6-6mm, and 4.5-10mm

Vertical Interval -- The time of the vertical retrace

Vertical Retrace -- Return of the electron beam to the top of a TV picture tube or a camera pickup device target at the completion of the field scan

Z

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