A

APERTURE:   The opening of a lens that controls the amount of light reaching the surface of the pickup device. The size of the aperture is controlled by the iris adjustment. By increasing the F-stop number (F/1.4, F/1.8, F/2.8, etc.) less light is permitted to pass to the pickup device.
 
ASPECT RATIO:   This is the ratio between the width and height of a television or cinema picture display. The present aspect ratio of the television screen is 4:3, which means four units wide by three units high. Such aspect ratio was elected in the early days of television, when the majority of movies were of the same format. The new, high definition television format proposes a 16:9 aspect ratio.

ATSC: Advanced Television System Committee. An American committee involved in creating the high definition television standards.
 
ATTENUATION:   This refers to signal loss in a transmission system.
 
AUTOMATIC IRIS:   A lens that adjusts automatically to allow the right amount of light to fall on the imaging device. There is a tiny motor and amplifier built in which receives a control signal from the camera to maintain a constant one volt peak to peak (pp) video level.

AWG: American wire gauge. A wire diameter specification based on the American standard. The smaller the AWG number, the larger the wire diameter.

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B
BACK FOCUS:  A procedure of adjusting the physical position of the CCD-chip/lens to achieve the correct focus for all focal length settings (especially critical with zoom lenses).
 
BACKLIGHT COMPENSATION:   Added circuitry that enables a camera to readjust the sensitivity of each pixel of the CCD which results in a uniform lighting condition.
 
BALANCED SIGNAL:   A video signal is converted to a balanced signal to enable it to be transmitted along a 'twisted pair' cable. Used in situations where the cabling distance is too great
 
BANDWIDTH:  The range of signal frequencies that a piece of audio or video equipment can encode or decode; the difference between the limiting frequencies of a continuous frequency band. Video uses higher frequency than audio, thus requires a wider bandwidth.

BNC: BNC stands for Bayonet-Neil-Concelman connector, and it is the most popular connector in CCTV and broadcast TV for transmitting a basic bandwidth video signal over a coaxial cable. See the accessories section for photo.

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C
C-MOUNT:   The standard screw mounting for 2/3" and 1" camera lenses. The distance from the flange surface to the focal point is 17.526mm. A C-mount lens can be used on a camera with a CS-mount by adding an adapter ring to reduce this distance to 12.5mm.
 
CCD:   Charge coupled device; It is light sensitive and forms the imaging device of most modern cameras. Size is measured diagonally and can be 1/3",1/2" or 2/3". There are two types, frame transfer and interline transfer.
 
CCIR:   Commite Consultatif International Radiotelegraphique. This is a standards committee of the International Telecommunications Union, who have made the technical recommendation for the European 625 line standard for video signals.
 
CCTV:   Closed circuit television. . Television system intended for only a select internal region of viewers, as opposed to open broadcast TV.
 
COLOR RENDERING INDEX (CRI):   Measures how well a light source is able to produce the actual color of a viewed object without causing a shift in the color.
 
COLOR TEMPERATURE:   Different ranges of white light are produced depending on the temperature that different forms of lighting produce. Color cameras must be able to compensate for these differences in color range to produce proper color reference on the monitor. See WHITE BALANCE.
 
COMPOSITE VIDEO:   The complete video signal comprising the sync and video information. The sync pulse should be 0.3 volts and the video signal should be 0.7 volts.
 
CRT:   Cathode Ray Tube. The main part of a normal monitor or television. Aka the screen.
 
CS-MOUNT:   A new generation of lenses designed for 2/3",1/2" and 1/3" cameras incorporating CS-mounts. The distance from the flange surface to the focal point is 12.5mm. CS-mount lenses cannot be used on cameras with C-mount configuration. These lenses are smaller and cheaper than the C-mount equivalents.

CS-to-C MOUNT ADAPTOR: An adaptor used to convert a CS-mount camera to C-mount to accomodate a C-mount lens. It looks like a ring 5 mm thick, with a male thread on one side and a female on the other, with 1'' diameter and 32 threads/inch. It usually comes packaged with the newer type (CS-mount) of cameras.

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D

DARK CURRENT: Leakage signal from a CCD sensor in the absence of incident light.

DECIBEL(dB):   A logarithmic measure of the ratio between two powers, voltages, currents, sound intensities, etc. Signal-to-noise ratios are expressed in decibels.

DEGAUSS: To demagnetize (a video screen)

DEPTH OF FIELD: The area in front of and behind the object in focus that appears sharp on the screen. The depth of field increases with the decrease of the focal length, i.e., the shorter the focal length the wider the depth of field. The depth of field is always wider behind the objects in focus.

DIFFERENTIAL GAIN: A change in sub-carrier amplitude of a video signal caused by a change in luminance level of the signal. The resulting TV picture will show a change in color saturation caused by a simultaneous change in picture brightness.

DIFFERENTIAL PHASE: A change in the sub-carrier phase of a video signal caused by a change in the luminance level of the signal. The hue of colors in a scene change with the brightness of the scene.
 
DIGITAL SIGNAL:   An analogue signal that has been converted to a digital form so that it can be processed by a micro processor.

DOT PITCH: The distance in millimeters between individual dots on a monitor screen. The smaller the dot pitch the better, since it allows for more dots to be displayed and better resolution. The dot pitch defines the reaslution of a monitor. A high-resolution CCTV or computer monitor would have a dot pitch of less than 0.3 mm.
 

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E
EIA:   The American 525 line standard for the video signal.

ENCODER: A device that superimposes electronic signal information on other electronic signals.

ENG CAMERA: Electronic News Gathering camera. Refers to CCD cameras in the broadcast industry.

EPROM: Erasable and programmable read only memory. An electronic chip used in many different security products that stores software instructions for performing various operations.

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F

F-NUMBER: In lenses with adjustable irises, the maximum iris opening is expressed as a ratio (focal length of the lens)/(maximum diameter of aperture). This maximum iris will be engraved on the front ring of the lens.

FIELD:   Each video image (`Frame') is composed of two fields. One field consists of the odd numbered lines in the frame and the other field consists of the even numbered lines. Each field viewed independently forms a picture but `interlacing', where they are joined together forms a frame.

FIXED FOCAL LENGTH LENSE: A lens with a predetermined fixed focal length, a focusing control and a choice of iris functions.
 
FOCAL LENGTH:   The distance betwen the secondary principal point in the lens and the plane of the imaging device. The longer the focal length, the narrower in the angle of view.
 
FRAME STORE:   An electronic method of capturing and storing a single frame of video. All slow scan transmitters include a frame store that holds the picture at the moment of alarm, while the control is being dialed up. When the link is confirmed, the picture is transmitted.
 
FRAME:   The combination of two interlaced fields, 25 frames are created every second.

 
G
GENLOCKING:   The process of aligning the data rate of a video image with that of a digital device to digitise the image and enter it into computer memory. The machine that performs this function is known as a genlock.

GAIN: Any increase or decrease in strength of an electrical signal. Gain is measured in terms of decibels or number of times of magnification.

GAMMA: A correction of the linear response of a camera in order to compensate for the monitor phosphor screen nonlinear response. It is measured with the exponential value of the curve describing the non-linearity. A typical monochrome monitor's gamma is 2.2, and a camera needs to be set to the inverse value of 2.2 (which is 0.45) for the overall system to respond linearly (i.e., unity).

GAMUT: The range of voltages allowed for a video signal, or a component of a video signal. Signal voltages outside of the range (i.e., exceeding the gamut) may lead to clipping, crosstalk or other distortions.

GRAY SCALE: A series of tones that range from true black to true white, usually expressed in 10 steps.

GROUND LOOP: An unwanted interference in the copper electrical signal transmissions with shielded cable, which is a result of ground currents when the system has more than one ground. For example, in CCTV, when we have a different earthing resistance at the camera, and the switcher or monitor end. The induced electrical noise generated by the surrounding electrical equipment (including mains) does not discharge equally through the two earthings (since they are different) and the induced noise shows up on the monitors as interference.
 

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H

HAD: Hole accumulated diode. A type of CCD sensor with a layer designed to accumulate holes (in the electronic sense), thus reducing noise level.

HDDTV: High definition digital television. The upcoming standard of broadcast television with extremely high resolution and aspect ratio of 16:9. It is an advancement from the analog high definition, already used experimentally in Japan and Europe. The picture resolution is nearly 2000×1000 pixels, and uses the MPEG-2 standard.

HDTV: High definition television. It usually refers to the analog version of the HDDTV. The SMPTE in the US and ETA in Japan have proposed a HDTV product standard: 1125 lines at 60 Hz field rate 2:1 interlace; 16:9 aspect ratio; 30 MHz RGB and luminance bandwidth.

HEADEND: The electronic equipment located at the start of a cable television system, usually including antennas, earth stations, preamplifiers, frequency converters, demodulators, modulators and related equipment. Helical scan. A method of recording video information on a tape, most commonly used in home and professional VCRs. Horizontal Drive (also Horizontal sync). This signal is derived by dividing sub-carrier by 227.5 and then doing some pulse shaping. The signal is used by monitors and cameras to determine the start of each horizontal line.

HORIZONTAL RESOLUTION: Chrominance and luminance resolution (detail) expressed horizontally across a picture tube. This is usually expressed as a number of black to white transitions or lines that can be differentiated. Limited by the bandwidth of the video signal or equipment.

HERRINGBONE: Patterning caused by driving a color-modulated composite video signal (PAL or NTSC) into a monochrome monitor.

HORIZONTAL RETRACE: At the end of each horizontal line of video, a brief period when the scanning beam returns to the other side of the screen to start a new line. Horizontal sync pulse. The synchronizing pulse at the end of each video line that determines the start of horizontal retrace.

HOUSINGS: Usually refers to cameras' and lenses containers and associated accessories, such as heaters, washers and wipers, to meet specific environmental conditions.

HS: Horizontal sync.

HUE (TINT, PHASE, CHROMA PHASE): One of the characteristics that distinguishes one color from another. Hue defines color on the basis of its position in the spectrum, i.e., whether red, blue, green or yellow, etc. Hue is one of the three characteristics of television color: see also Saturation and Luminance. In NTSC and PAL video signals, the hue information at any particular point in the picture is conveyed by the corresponding instantaneous phase of the active video subcarrier.

HUM: A term used to describe an unwanted induction of mains frequency. Hum bug. Another name for a ground loop corrector.

HYPER-HAD: An improved version of the CCD HAD technology, utilizing on-chip micro-lens technology to provide increased sensitivity without increasing the pixel size.

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I
INFRA RED LIGHT:   The wavelength of light produced above the visible part of the spectrum.
 
INTERLACE:  The pattern described by two separate field scans when they join to form a complete video frame. As the video picture is transmitted, the first field picks up even-numbered scan lines - the second, odd-numbered ones. The two interleave together to form a single, complete frame.
 
INTERNAL SYNC:   The internal generation of sync pulses in a camera using a crystal controlled oscillator. This is needed on non-mains powered cameras.
 
IRIS:   The mechanism that can be adjusted to vary the amount of light falling on the imaging device.
 
INTERLACE:  The pattern described by two separate field scans when they join to form a complete video frame. As the video picture is transmitted, the first field picks up even-numbered scan lines - the second, odd-numbered ones. The two interleave together to form a single, complete frame.
 
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J
K

K FACTOR: A specification rating method that gives a higher factor to video disturbances that cause the most observable picture degradation.

L

LENSE: An optical device for focusing a desired scene onto the imaging device in a CCTV camera.

LEVEL: When relating to a video signal it refers to the video level in volts. In CCTV optics, it refers to the auto iris level setting of the electronics that processes the video signal in order to open or close the iris.

LINE LOCKED:   The sync pulses of cameras are locked to the AC mains frequency.
 
LINE POWERED:   A camera in which the power is supplied along the same coaxial cable that carries the video signal.
 
LOOP FRAME STORE:   The principle is that a series of video frames is compressed and stored in a continuous loop. This records a certain number of frames and then records over them again and again until an alarm signal is received. When this happens it carries on recording for a dozen frames or so and then stops. This means that frames before and after the incident are recorded. This eliminates the boring searching through hours of video tape and concentrates on the period of activity.

LUMEN [lm] . A light intensity produced by the luminosity of 1 candela in one radian of a solid angle.
 
LUMINANCE:  Scene brightness.
 

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M

MOD: Minimum object distance. Feature of a fixed or a zoom lens that indicates the closest distance an object can be from the lens's image plane, expressed in meters. Zoom lenses have MOD of around 1 m, while fixed lenses usually much less, depending on the focal length.

MORIE PATTERN: An unwanted effect that appears in the video picture when a high-frequency pattern is looked at with a CCD camera that has a pixel pattern close (but lower) to the object pattern.

MONOCHROME: Black-and-white video. A video signal that represents the brightness values (luminance) in the picture, but not the color values (chrominance).

MULTIPLEXER:   An electronic system that can accept a number of camera inputs and record them virtually simultaneously. They can also provide multi screen displays with four, nine, sixteen etc. cameras on the screen at once. Multiplexers can be used to transmit up to sixteen pictures down a single video line whether it is a coaxial cable, microwave, infrared link etc. This requires a multiplexer at each end of the line.
 

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N
NOISE:   Any unwanted signal that affects the video signal. Usually random electrical energy or interference. In video, noise can produce a random salt and pepper pattern over the picture. Heavy video noise is called snow.
 
NTSC:   National Television Systems Committee of the Electronics Industries Association (EIA) which prepared the NTSC format specifications approved by the Federal Communications Commission, for US commercial colour broadcasting. `NTSC' also refers to a colour television format having 525 scan lines, a field frequency of 60 Hz, a broadcast bandwidth of 4 MHz, line frequency of 15.75 KHz, frame frequency of 1/30 of a second, and a colour subcarrier frequency of 3.58 MHz.
 

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O
OVERSCANNING:   A technique used in consumer display products that extends the deflection of a CRT's electron beam beyond the physical boundaries of the screen to ensure that images will always fill the display area. See also underscanning.
 
P
PAL:  Phase Alternation Line; the European standard colour television system, except for France. PAL's image format is 4:3, 625 lines, 50 Hz and 4 MHz video bandwidth with a total 8 MHz of video channel width.
 
PAN TILT ZOOM (PTZ):   A device that can be remotely controlled via a joystick or keyboard device to provide both vertical and horizontal movement for a camera, with zoom.
 
PEAK TO PEAK:   The measurement of a video signal from the base of the sync pulse to the top of the white level. For a full video signal this should be one volt.
 
PIXEL:   Picture element.
 
PRE-SET CONTROLLER:   A function contained within a telemetry system that, on receipt of a signal, causes a particular camera to pan, tilt and zoom to a predetermined field of view. Most systems can accommodate up to sixteen preset positions for each camera. This is an especially useful feature on larger systems with alarmed areas.
 

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Q
QUAD SCREEN:  Display where 4 cameras are viewed on the same screen, each camera image occupying a quarter of the display area. Other `multi screen' modes are possible such as 9, 16 and 25 way. The splits do not always have to be equal and other configurations can be possible.
 
R
REAL TIME RECORDING:   Refers to the top speed of a video recorder; governed by the monitor - pictures are available as fast as the video can accept them.
 
REMOTE SWITCHER:   A video switcher which is connected to the camera cables and which contains the switching electronics. This unit may be remotely located and connected to a desk top controller by a single cable for each monitor.
 
RESOLUTION:   Number of pixels per unit of area. A display with a finer grid contains more pixels and thus has a higher resolution, capable of reproducing more detail in an image.

RG-11: A video coaxial cable with 75-W impedance and much thicker diameter than the popular RG-59 (of approximately 12 mm). With RG-11 much longer distances can be achieved (at least twice the RG-59), but it is more expensive and harder to work with.

RG-58: A coaxial cable designed with 50-W impedance; therefore, not suitable for CCTV. Very similar to RG-59, only slightly thinner.

RG-59:: A type of coaxial cable that is most common in use in small to medium-size CCTV systems. It is designed with an impedance of 75-W. It has an outer diameter of around 6 mm and it is a good compromise between maximum distances achievable (up to 300 m for monochrome signal and 250 m for color) and good transmission.
 

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S

S/N RATIO: See Signal-to-noise ratio.

SCENE ILLUMINATION:   The density of light in LUX falling on the area to be viewed. For best results the ratio of the lightest to the darkest areas should not be more than a factor of two.
 
SCREEN SPLITTER:   A term usually used for a device that can combine the views from two cameras on a single screen. The split can be arranged horizontally, vertically or one picture inserted in another.
 
SECAM:   Sequential Couleur A Memoire (sequential colour with memory), the French colour TV system also adopted in Russia. The basis of operation is the sequential recording of primary colours in alternate lines. The image format is 4:3, 625 lines, 50 Hz and 6-MHz video bandwidth with a total 8 MHz of video channel width.
 
SIGNAL TO NOISE RATIO (SNR):   A measurement of the noise level in a signal expressed in dB (decibels). In a video signal values from 45dB to 60dB produce an acceptable picture. Less than 40dB is likely to produce a 'noisy' picture.

SMEAR: An unwanted side effect of vertical charge transfer in a CCD chip. It shows vertical bright stripes in places of the image where there are very bright areas. In better cameras smear is minimized to almost undetectable levels.

SWITCHER: See video switcher
 
SVHS or SUPER VHS:   A higher quality extension of the VHS home videotape format, featuring higher luminance and the ability to produce better copies.
 
S-VIDEO:  Type of video signal used in the Hi8 and SVHS videotape formats. S-video transmits luminance and colour portions separately, using multiple wires, thus avoiding the colour encoding process and its inevitable loss of picture quality.
 

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T
TELEMETRY:   The system by which a signal is transmitted to a remote location in order to control CCTV equipment eg. to control pan and tilt and zoom functions, switch on lights, move to preset positions etc. The controller at the operating position is the transmitter and there is a receiver at the remote location. The signal can be transmitted along a simple 'twisted pair' cable or along the same coaxial cable that carries the video signal.

TERMINATION: This usually refers to the physical act of terminating a cable with a special connector, which for coaxial cable is usually BNC. For fiber optic cable this is the ST connector. It can also refer to the impedance matching when electrical transmission is in use. This is especially important for high frequency signals, such as the video signal, where the characteristic impedance is accepted to be 75-W.
 
TIME LAPSE VCR:   A type of video recorder that can be set to record continuously over long periods. This can be anything from three hours to 480 hours, achieved by the tape moving in steps and recording one frame at at time. This means that if set to record over long periods much information can be lost. On receipt of an alarm signal these machines can be automatically switched to real time mode.

TRACKING: The angle and speed at which the tape passes the video heads.
 
TOUCH SCREEN CONTROL:   A system by which all the camera controls are displayed on the screen of a special monitor. To control any function simply requires the screen to be touched at the appropriate symbol which can be to select a camera or pan, tilt and zoom. The system is computer driven and can include maps, diagrams etc. that are automatically displayed according to the alarm received.
 

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U

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.

UNDERSCANNING:   A technique generally used by some TV and video systems as a way of ensuring that the complete image is always visible within a display area; the opposite of overscanning.
 

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V
VCR:   Video Cassette Recorder aka video, video recorder.

VIDEO GAIN: The range of light-to-dark values of the image that are proportional to the voltage difference between the black and white voltage levels of the video signal. Expressed on the waveform monitor by the voltage level of the whitest whites in the active picture signal. Video gain is related to the contrast of the video image.

VIDEO IN-LINE AMPLIFIER: A device providing amplification of a video signal.

VIDEO MOTION DETECTION:   A method of detecting movement in the view of the camera by the electronic analysis of the change in picture contrast.

VIDEO SWITCHER: A device for switching more than one camera to one or more monitors manually, automatically or upon receipt of an alarm condition.
 

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W
WHITE BALANCE:   The ability of a color camera to automatically compensate for differences in the range of white light produced by different forms of lighting. This is necessary to produce proper color reference on the monitor. Most color cameras have auto white balance that can adjust between 2800 and 7000 degrees Kelvin.
 
WHITE LEVEL:   The brightest part of a video signal corresponding to approximately 1.0 volt.
 
X
Y
Y/C VIDEO:   See S-video.
 
Z

Z: In electronics and television this is usually a code for impedance.

ZOOM LENSE: A camera lens that can vary the focal length while keeping the object in focus, giving an impression of coming closer to or going away from an object. It is usually controlled by a keyboard with buttons that are marked zoom-in and zoom-out.

ZOOM RATIO: A mathematical expression of the two extremes of focal length available on a particular zoom lens.

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