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CCTV Glossary


Access control system:
an electronic system that allows, restricts and tracks the movement of people through entry/exit points in a site.  Programmable electronic keys, cards etc. with readers are used to achieve this.

AGC Automatic Gain Control:
is circuitry in a camera which boosts the video signal (including the noise).  It becomes operational when the light level is low.

Alarm Activated VCR:
After pressing "record", a normal VCR takes about 20 seconds before it starts recording usable pictures.  With an alarm activated recorder it can be set so that the tape is ready to start recording in about one second.  The signal to begin recording can be from an alarm or any other input.

Alarm Interface:
is a facility which allows external alarms like PIR's, reed switches, vibration sensors etc. to be connected to the CCTV switcher so that a nominated camera is switched on when an alarm signal is received.

ALC Automatic Light Compensation:
is a setting in an auto iris lens to control the iris opening.  It can be adjusted between peak and average to respond to the bright part of the scene (peak setting) or the average value of the video signal (average setting).

Algorithms:
are complex mathematical formulae or rules used to solve problems.  In CCTV, they are used to achieve digital compression of a video picture.

Alkaline Battery:
is a type of DC power source with a longer life compared to the standard battery.  It cannot be recharged.

Amplitude:
refers to the strength of the video signal at a point and is measured in volts.

Angle of View:
represents the area of the scene (maximum horizontal and vertical angle) that can be seen through a lens.  It is measured in degrees.

Aperture:
the light gathering area of a lens, controlled by the iris.

Aspect Ratio:
is the ratio between the horizontal and the vertical lengths of the video picture.  The aspect ratio for NTSC and PAL is 4:3.

Attenuation:
This refers to signal loss in a transmission system of light or an electrical signal and is usually measured in decibels. 

Audible Detector:
is a device which detects sound.  In CCTV, it can be interfaced with a switcher so that a nominated camera is switched on when the detector is activated.

Audio Switching:
is a device which can switch between various audio inputs either manually or sequentially.  Many matrix switchers incorporate this feature.

Auto Balance:
is a system of detecting and automatically correcting errors in the amplitude of color signals.

Auto Iris:
is a diaphragm which is inbuilt in a lens to automatically control the amount of light falling on the chip.  The tiny motors in the lens open or close the diaphragm, depending upon the amplitude of the video signal.

Automatic Pan:
is a feature of a pan tilt or pan only head which allows the head to continuously move (pan) left and right between two fixed points.  These fixed points can be set by adjusting the limit switches in the head.

Average Video Signal:
represents the average light level of the whole picture used to open or close the automatic iris in the lens.

Back Focus:
is a fine mechanical adjustment in the camera which moves the CCD chip or the lens mount (depending upon camera brand) to ensure the chip is placed at the exact focal point of the lens.

Backlash:
is an error present in a pan tilt head due to the play in the mechanical components like gears, pulleys etc.  This results in the Pan Tilt head not stopping instantaneously.  This error is critical in pre set PTZ cameras and is measured in degrees.

Balanced Cable:
is a type of cable in which the signal is divided over a pair of cables and travels in opposing polarity.  This reduces interference allowing transmission over longer distances.

Bandwidth:
is the range of frequencies that pass through an electrical/electronic amplifying, processing or transmission unit without attenuation or loss.

Barrel Distortion:
is a distortion in the monitor due to non uniform scanning which causes the image to bulge outwards like a barrel.

Beam Angle:
is the angular beam width of a conical beam of light and is measured in degrees.

Blanking Pulse:
is a black pulse added during the fly back period to make the video signal invisible on the screen.

BNC Connector:
is a type of connector used to interconnect two coaxial cables or connect a cable with other CCTV components.

Bridging Switcher:
is a type of sequential switcher which has two outputs.  The sequencing output sequences all the camera inputs whereas the other output is a spot output where any camera can be called up for extended viewing.

Brightness:
represents the intensity of illumination of the reproduced picture.

Brightness Control:
is a control in the monitor which does not change the amplitude of the video signal but increases or decreases the illumination of the phosphors on the screen.

Broadcast Camera:
is a high quality camera using three CCD chips.  It is used extensively in the professional broadcasting industry.

C-Mount:
is a lens mount with 17.526 mm back flange.  Back flange is the distance between the lens mounting surface and the CCD chip.

Cable Compensated Amplifier:
High frequency video signals are attenuated when transmitted through cables.  A cable compensated amplifier boosts the high frequency signals depending upon the cable distance.  This ensures minimum video loss.

Cable Core:
is the central part of the cable which actually carries the video, control or power signals.  It can be made up of a single conductor (solid core) or a number of electrical wires.

Cable Jacket:
is the outer protective coating which covers the core of the cable.

Cable Tray:
is a long tray installed in many sites which allows cables to be economically laid out.

Camera:
is an electronic device which converts light into an electrical signal.

Camera Controller:
controls the different functions of the pan tilt head and the zoom lens.  It is also known as the PTZ controller.

Candela:
a new unit which replaces the candle and is a measurement of luminous intensity.

Cathode Ray Tube (CRT):
is a tube in the monitor containing a heated cathode which emits a beam of electrons focused on a phosphor coated surface.  The surface glows depending upon the intensity of the beam.  The deflection circuitry in the tube controls the movement of the beam.

CCD Charge Coupled Device:
is a solid state device in a camera that converts light falling on it into an electrical signal.

CCD Iris:
is a feature in modern CCD cameras by which the iris function is performed by the CCD chip itself.  This eliminates the need for an auto iris lens.  The CCD iris can handle minor light fluctuations only and therefore is not recommended for most outdoor applications.

CCTV Lens:
(Closed Circuit Television Lenses) Today the term often means the lenses for small CCD cameras used in a wide range of applications.

CCIR International Radio Consultative Committee:
recommends a format of 625 lines per frame and a transmission speed of 25 frames per second.

Celsius:
is the metric unit for measuring temperature.  In this scale, the boiling point of water is 100 degrees.  In the USA, the unit used to measure temperature is Fahrenheit.

Channel Separation:
When signals are multiplexed at different frequencies for transmission, then the separation between these frequencies is called channel separation.  Poor separation can lead to cross talk.

Chromatic Aberration:
is an error in lenses which causes the focal point to be scattered.  This occurs because different wavelengths of light bend differently through a lens.  A combination of lenses are required to minimize this error.

Chrominance Signal:
is that part of the video signal which contains the color information.  In S-VHS, this signal is transmitted along a separate cable.  In a composite video signal, the chrominance signal is multiplexed at a higher frequency and sent along the same cable.

Color Stripe Filter:
is a type of filter placed in front of a color CCd chip.  It breaks up light into the basic colors - red, green and blue which are then directed to separate pixels in the CCD chip.

Common Sync Generator:
is a device used to synchronize cameras.  It generates synchronizing pulses that are sent to all cameras connected to it by coaxial cable.

Composite Video:
is a standard signal format in CCTV which contains the video signal, the horizontal and vertical sync pulses and the blanking pulses.  The sync pulses are 0.3 volts and the video signal is 0.7 volts.

Concave:
is a type of optical lens in which the light rays passing through it are made to diverge by the inward bulge of the glass surface.

Conduit:
is a plastic or metallic tube which is used to conceal, protect or secure cables.

Connector:
a device used to interconnect cables or connect cables to various equipment.

Contrast:
is the difference in the intensity between the black parts and white parts of the picture on the monitor.

Contrast Control:
is a control in the monitor which changes the contrast by increasing or decreasing the amplitude of the video signal.

Covert:
is a mode of CCTV surveillance in which the camera and lens are hidden and can not be seen.

Convex:
is a type of optical lens in which the light passing through it are made to converge by the outward bulge of the glass surface.

Crimping:
is a process of connecting a cable to a connector without screwing or soldering using a special tool.  In crimping a BNC connector, the center pin of the connector is uniformly pressed against the cable core.  To ensure a proper connection, a good crimping tool is needed.

Cross Talk:
is the noise generated by the interference between adjacent (in terms of signal frequency) video, audio and data channels in a multiplexed signal.

CS Mount:
is a lens mount with 12.5 mm back flange.  Back flange is the distance between the lens mounting surface and the CCD chip.

Decibels:
is a logarithmic ratio used to compare characteristics of electrical signals.

De-multiplexing:
is the process of separating the different video, audio or data channels which were multiplexed at the source.

Depth of Field:
is the distance between the nearest and furthermost points of the scene which appear in sharp focus.  It depends upon the F-stop and focal length of the lens.

Dielectric:
is a material which insulates the solid center core of a coaxial cable from the shield.  The thickness of the dielectric affects the impedance of the cable.

Digital Signal:
An analogue signal that has been converted to a digital form so that it can be processed by a micro processor.

Dome:
is a type of camera housing made of smoked or tinted plastic.  It is excellent for discreet surveillance and is also available with in built pan tilt heads.

DSP Chip:
Digital Signal Processing chip is a solid state device which converts an analogue video signal into a digital video signal.  It is used in digital cameras and also in computers to digitize video images.

Duplex:
is a system which can handle simultaneously two channels of video, audio or data signals.

Dwell Time:
is a feature in a switcher.  It is the time period a picture from a given camera remains on the monitor before being replaced by a picture from the next camera.  Switchers may have fixed or programmable dwell times.

EASS Electron Article Surveillance System:
is used in retail shops to electronically tag the merchandise to prevent shop thefts.  A CCTV system can be interfaced with an EASS system so that the appropriate camera is switched on when an offense occurs.

EIA:
is a scanning method specified by the Electrical Industry Association.  RS-170 is the standard for the monochrome and RS-170A is the standard for color.

Electrical Filter:
is a type of electrical circuitry designed to limit transmission of certain frequencies.

Electron Beam:
is a concentrated flow of electrons in a nominated direction.

Electronic Shutter Speed:
see Shutter Speed

Shutter Speed:
is the speed at which the charge is read out from the CCD chip.  The factory setting is 1/50 sec (PAL) or 1/60 (NTSC) and can be increased up to 1/500,000 sec depending upon the camera brand.  It can be changed by using dip switches or in some cases by the in built menu in the camera.

EMI Electro Magnetic Interference:
is a interference which is usually caused by any electrical equipment radiating electro magnetic frequencies.

Ergonomics:
is the study of man, machine and the environment to achieve maximum efficiency.

Event Recorder:
is a type of recorder that is normally maintained in pause mode and starts recording only when activated by an alarm.

Extruded Aluminum:
is aluminum processed through a die and shaped for use to construct housings for CCTV applications.

Extruded Plastic:
is a process in which smoked or tinted plastic is processed and shaped to construct dome housings.

F-stop:
is the ratio between the focal length of the lens and the effective diameter of the iris opening.  It indicates the light gathering ability of the lens.

Fast Lens:
is a lens which can gather and transmit more light to the camera.  A fast lens has a larger iris opening and therefore a smaller F-stop.

Fast Scan Video:
is a method of sending video images over the telephone network to any part of the world. The update rate presently is not real-time but is improving continuously.

Fence Disturbance Sensor:
is a type of sensor installed around the perimeter fence in a site to detect any intrusion. There are many types of fence disturbance sensors available. In CCTV it can be interfaced with a switcher. to switch a nominated camera for extended viewing.

Fiber Optics:
is a method of modulating video, audio or data with a light beam and transmitting it along a glass core.

Field:
is one half of a frame and consists of 312.5 (PAL) and 262.5 (NTSC) lines. Odd and even fields are combined to form a single frame.

Field of View:
is the height and width of the view that can be seen through a lens.

Fixed Lens:
is a lens with a fixed focal length. A wide range of fixed lens are available to suit different applications e.g. 2.6mm, 4.8mm, 8mm, 16mm, 25mm, 75mm etc.

Flange Back:
Flange back is the distance from the surface (flange) where the lens comes in contact with the camera to the focal point

Flexi Conduit:
is a flexible PVC conduit which is used at the camera point to enclose loose cables between the camera and the junction box or wall.

Fluorescent Lamp:
is a type of artificial light source in which the mercury vapor generated by a low wattage arc strikes the phosphor material to emit light. It is popularly used in indoor applications.

Fly Back Period:
is the time taken to move from the end of a field, frame or line to the start of the next field, frame or line. It is also called the retrace period.

Focal Length:
is the distance between the optical center of a lens and the point of focus. It is usually measured in mm or inches.

Focus Ring:
is a ring on a lens which is rotated to obtain correct focus. It is available only in manual iris lenses.

Foot Candle:
is a unit of luminance. 1 foot candle = 1 lumen of light incident on 1 sq. ft of surface area.

Frame Interline Chip:
is a type of CCD chip which is expensive to manufacture and is currently used in broadcasting video cameras. It overcomes many shortcomings of the existing CCD chips used in CCTV cameras.

Frame Switching:
is a process used in multi-plexers or multi-recorders in which a frame is picked up from each camera in turn.

Frame Store:
is an electronic device used to capture and digitally store a video image. It can be an independent unit or in built in other equipment like fast scan video transmitters or video motion detectors.

Frame Transfer Chip:
is a type of CCD chip in which the pixels have a dual role of sensing the light and transferring the charge. This causes picture smearing, a major shortcoming of this chip.

Frame:
is the basic unit of a moving picture. A frame contains 625 lines (PAL) or 525 lines (NTSC).

Gamma Correction:
is a correction built into the camera to adjust for the brightness characteristic of the monitor. The gamma value ranges from 0.6 to 1.0

Geometric Distortion:
is an error which causes the reproduced picture to be geometrically different from the original picture.

Graded Index Cable:
is a type of fiber optics cable which reduces transmission error by means of a cladding having a graded index of refraction.

Ground Loop Current:
is an AC current produced in a video cable when the two ends of the cable do not have the same ground potential.

Ground Loop Insulator:
is an isolation transformer which can eliminate ground loop currents by removing any direct connection between the inputs and outputs.

GUI Graphical User Interface:
interfaces the computer with the matrix switcher. Hot areas on the computer screen can be programmed to activate a matrix switcher, VCR etc. It helps in making the CCTV system more user friendly.

Hertz:
is a unit of measuring frequency. 1 Hertz = 1 cycle per second.

Homing Sequential Switcher:
is a type of switcher used for small systems. It has only one output.

Horizontal Resolution:
is the number of vertical lines which can be resolved in a picture. It depends upon the number of pixels in a chip.

Horizontal Shift Register:
is a part of the CCD chip to which the charge from the pixels is transferred line by line. This charge is then converted into an analogue video signal.

Housing:
Outdoor cameras need housings to protect them from heat, cold and moisture. Indoor cameras need housings for disguise or to protect against vandalism.

Image Intensified Camera:
is a type of camera coupled with an image intensified tube which generates additional photons. This tube allows the camera to be used in low light areas.

Image Intensifier:
is a device which intensifies light by using light sensitive phosphor screens. It is used to improve camera performance under low light conditions.

Impedance:
is the input and output characteristic of any electrical system and is measured in ohms. For maximum signal transfer, the input and output impedance should be the same. CCTV systems have a 75 ohm impedance.

Incandescent Light:
is a type of artificial light source invented by Thomas Eddison in 1862. It has a good spectral response but low life and efficiency.

Index of Refraction:
is a ratio between the angle of incidence to the angle of refraction of light. It depends upon the density of a medium. A denser medium will have a higher index of refraction and will also bend the light more.

Infrared Detector:
is a type of alarm which works on the principle of infrared light to detect movement in a zone

Infrared Illuminator:
is a type of light source which emits light in the infrared frequency range.

Infrared light:
The wavelength of light produced above the visible part of the spectrum.

Infrared Link:
is a type of transmission medium in which video, data or audio are modulated with infrared light and then transmitted into air to a receiver in a remote location.

Infrared Radiation:
is electromagnetic radiation with a wavelength of more than 750 nanometers. It is not visible to the human eye.

Internal Sync:
The internal generation of sync pulses in a camera using a crystal controlled oscillator. This is needed on non-mains powered cameras.

Interference:
is external energy which interferes with an electrical signal causing picture distortions.

Interlacing:
is the process of combining even and odd fields to form a frame.

Interline Transfer Chip:
is a type of chip used in most of the current CCTV cameras as the charge read out method is more efficient than a frame transfer CCD chip . Vertical streaking and small pixel size are some of the shortcomings.

Iris:
is a part of a lens that can be adjusted to vary the amount of light passing through the lens and falling on the CCD chip.

Iris Plug:
is a type of connector which connects the camera to an auto iris lens to provide power to the iris motor and to send the video signal which controls the iris opening.

ISDN Integrated Services Digital Network:
is a type of telephone network which accepts digital signals.

Joystick:
is a control device in the form of a stick in a PTZ controller used to control the pan and tilt movement of a pan tilt head.

LD Laser Diode:
is a type of light source which generates a single frequency in the high end of the infrared spectrum and has a bandwidth of 1000 MHz. It is used in fibre optics and infrared links.

Lead Acid Battery:
is a type of DC power source which is similar to a car battery. It is generally used in temporary installations with DC cameras.

LED Light Emitting Device:
is a type of light source which generates an infrared frequency when stimulated by electricity. It is used in fiber optics , infrared links and as an infrared light source for monochrome cameras.

Lens Calculator:
is a calculator provided by many lens manufacturers to help calculate the focal length of the lens that will provide the required scene.

Lens Hunting:
is a field problem in which the iris opens and shuts alternatively. A correct ALC adjustment in the lens could rectify the problem.

Lens Mount:
see C-mount or CS-mount.

Lens Wheel:
see lens calculator.

Light:
is electromagnetic radiation between 400 nm and 750 nm which is detectable by the human eye.

Light Sensor:
is a device which is activated by a pre-set amount of light falling on it. It can be used to switch infrared illuminators On / Off.

Limit Switch:
is a device placed inside or outside the Pan Tilt head and used to limit the angles of pan and tilt.

Line:
is the basic unit of a frame or field containing the charge which is proportional to the light falling at various points on the scanning line.

Line Locked:
Video signal is synchronized in the cameras by the AC 60 Hz frequency.

Line Powered:
Camera receives operating power along the same coaxial cable that carries the video signal back to the monitor or recorder.

Loop Frame Store:
A short amount of video is recorded, then recorded over again and again until an alarm triggers it, then the recorder records the segment and stops. This way only the period of alarm has to be viewed. Saves lots of searching through hours of non-event video.

Looping Switcher:
is a type of switcher with looping outputs. These outputs allow the camera to be connected to another device without affecting the usage of the switcher.

Lumen:
is a measurement of light which indicates the amount of light radiated by a one candela light source.

Luminous Flux:
is the rate of flow of light.

Luminance Signal:
is that part of the video signal which contains the information on the brightness of the picture.

Lux:
is an international unit of illumination. It is the amount of uniform light falling on an area of 1 square meter and is measured in lumen per sq. meter.

Matrix Switcher:
is a type of switcher which allows a single input to be switched to many outputs. Matrix switchers are used in large CCTV systems and have many powerful features.

Mercury Vapor Lamp:
is a popular type of artificial light source which emits a blue-white light. Used extensive for commercial lighting.

Micron:
is a unit of measuring length. 1 micron = 10 -6 meters

Microwave Detector:
is a type of alarm which uses microwaves to detect movement in a zone.

Microwave Link:
is a type of transmission medium in which video, data or audio is modulated with a microwave frequency and then transmitted to a receiver in a remote location.

Mimic Panel:
is a panel which shows the layout of a site with the camera positions highlighted. By interfacing it with a switcher, the operator can switch any camera to the monitors from the mimic panel itself.

Minimum Scene Illumination:
is a specification shown in most camera data sheets and indicates the minimum light required at the scene to provide a reasonable picture on the monitor.

Modem:
is derived from the term 'modulator -demodulator' and is used to convert a digital signal into an analogue signal so that it can be transmitted via the PSTN telephone network.

Modulate:
is a method in which a signal to be transmitted is mixed with a high frequency carrier signal .

Monitor:
The TV type screen you look at to watch your cameras. They come in black and white and color and 9" and 13" sizes so that they can be racked in quantity in consoles.

Motorized Iris:
is a type of iris control in which the iris motor is controlled from a remote location.

Mount:
Mounts place the camera into the exact position needed to view the intended scene. They mount to walls, ceilings or floor on pedestals. They must support the weight of the camera, lens, housing and any pan-tilt used.

Multi Core Cable:
is a type of cable which has many cores enclosed in one outer jacket. In CCTV it is normally used to transmit control signals.

Multimode Cable:
is a cheaper type of fiber optics cable which allows a light beam to travel by more than one path thus causing transmission distortion.

Multiplexing:
is a process whereby many cameras are switched frame by frame. This frame switching can be used in applications like multi-viewing, multi-recording etc.

Neutral Density Filter:
is a type of filter used with lenses which reduces light of all wavelengths equally.

Noise:
is an unwanted signal generated by every electronic component. The noise in a video signal causes a grainy or snowy effect on the image.

NTSC National Television System Committee:
is a color television system and the standard used in the USA and Japan. NTSC has 525 horizontal scanning lines and 60 fields per sec.

Omni Directional Transmitter:
is a transmitter which sends the signal in all directions.

Optical Filter:
is a type of filter used in optics which selectively allows light of different frequencies to pass through.

Oscilloscope:
is a device which visually displays the wave form of any electrical signal on a screen. In CCTV, it is used trouble shooting and making adjustments of various components.

Pan Tilt:
Mechanism for controlling the position of a camera remotely. You can control the horizontal and vertical movement of the camera. Combined with zoom control, you can sweep large areas with one camera and zoom in on areas of interest.

Persistency of Vision:
The retina of the human eye retains an image for 40ms. This characteristic is called persistency of vision and is used to make a picture appear continuous by flashing images on the retina at a rate faster than 24 images per sec.

Phase Adjustment:
is a camera adjustment used to synchronize all the cameras in the system by altering the phase of the power supply.

Phase Angle:
is the angle at any point of the sine wave of an AC power supply and varies between 0 to 360 deg. over a cycle.

Phosphor:
is a material which is capable of emitting light. It is used in fluorescent lamps, monitors etc. The duration of the emission depends on the type of phosphor.

Photon:
is the basic unit of light.

Picture Tearing:
occurs when the horizontal sync pulses are distorted or lost and the monitor is unable to latch on to them causing the horizontal lines to be displaced in a random manner. This is seen as a tearing of the picture on the monitor.

Pincushion Distortion:
is a type of distortion caused due to non uniform scanning in the monitor which makes the picture to bulge inwards.

Pinhole Lens:
is a small lens with a diameter of 1.5mm to 9.5mm used for covert surveillance.

Pixel (picture element):
is the basic unit of a CCD chip which accumulates charge depending upon the amount of light falling upon it. A typical CCD chip has over 300,000 pixels.

Polarizer:
is a type of filter which reduces glare by intercepting reflected light from surfaces like water , glass. etc.

Polycarbonate Glass:
is a type of toughened glass which can be used in housings for use in high vandal areas.

Polyethylene:
is a type of plastic used to make outer jackets for cables.

Potentiometer:
is an electronic component in which the resistance can be changed by a movable contact point. It is used in pan tilt heads and zoom lenses to record pre-set positions.

Power Line Interference:
is a type of interference caused by main power lines and usually seen as horizontal bands on the monitor.

Preamplifier:
is a type of amplifier used to increase the output of a low level source allowing the signal to be processed by other devices.

Pre set:
is a term used in CCTV to define pre determined positions of a pan tilt head and zoom lens.

Pressure Mat:
is a device which is activated by the application of pressure and is used to open doors, gates etc. It can also activate the switcher to bring the nominated camera up for extended viewing.

Primary Color:
is a basic color which cannot be obtained by mixing other colors. Red, green and blue are the three primary colors which can be mixed to produce other colors.

PSTN Public Switched Telephone Network:
is a type of analogue telephone network currently in use all over the world.

PTZ controller:
is a device used to control the movement of the pan tilt head and zoom lens from a remote location.

Quad:
is a device which uses digital video to display pictures from 4 or more cameras on a single monitor.

Real Time Video:
is a picture with more than 24 frames per sec and therefore looks continuous.

Receiver Driver:
is a part of the matrix switcher placed at the camera point and connected to the main switcher by a twisted pair cable. It is used to decode the incoming control signals for the Pan Tilt Zoom functions.

Reed Switch:
is a type of alarm activated when the contact is opened or closed . It is widely used with doors, windows, roller shutters etc. and can also activate a switcher to bring the nominated camera up for extended viewing.

Regulated Power Supply:
is a type of DC power supply in which the ripple factor is minimal.

Remote Head Camera:
is a type of camera in which the CCD chip is separated from the camera body by cable. It is used in applications where the amount of space is limited.

Resolution:
is a measure of picture definition and clarity and is represented by number of lines. Greater the number of lines, higher the resolution.

RG-11:
is a type of coaxial cable with a thicker center core and used for transmission of video signals up to 550m.

RG-59:
is a type of coaxial cable used for transmission of video signals up to 230m. It is the most popular cable used in CCTV.

Ripple Factor:
is the amplitude variation present in a DC power supply due to insufficient filtering . A large variation can damage a DC camera.

RS-232:
is a communication protocol used for communication between microprocessor based devices.

Salvo Switching:
is a feature in matrix switchers. On command from the matrix switcher or an alarm event. a group of cameras can be switched simultaneously onto a group of monitors.

Scene Illumination:
Lighting within the whole area of the camera view. The ratio of the lightest to the darkest areas should be no greater than a factor of two.

Screen Splitter:
A device to put two camera signals onto one monitor, either side by side, top and bottom or picture in picture.

SECAM Sequential Coluleur A'Memorie:
a color television system used in France and a few other countries.

Sensitivity of a Camera:
is the minimum light level required at the CCD chip which will generate a usable video picture. It is measured in lux.

Sequential Switcher:
is a type of switcher that allows multiple cameras to be displayed or recorded one at a time.

Shield:
is a copper braid which covers the dielectric and center core of a coaxial cable. It protects the video signal from EMI.

Signal Loss:
is a reduction in signal strength expressed in decibels.

Signal to Noise Ratio: (S/N Radio)
It is the ratio between the signal voltage and the noise voltage generated by an electronic circuit. It is measured in decibels (dB).

Simplex:
is a system which can handle only one channel of video, audio or data signal.

Single Mode Cable:
is an expensive type of fiber optic cable with a narrow glass core which allows only a single path for signal transmission.

Silicon Wafer:
is a semiconductor material on which the CCD chips are etched.

Snow:
is a fault in the picture, appearing as small dots on the monitor and is caused by heavy noise in the video signal.

Sodium Vapor Lamp:
is a type of artificial light source which is very efficient and uses sodium vapor to produce a yellow-orange light.

Spectral Response:
is the sensitivity of a device to different light frequencies.

Standard Angle Lens:
is a type of lens which provides a view having the same proportions as seen by the human eye. It has a magnification ratio of 1.

Step Down Transformer:
is a transformer used in power supplies to step down or lower the main line voltage. The ratio between the number of turns of the primary coil to the secondary coil determines the step down voltage.

Stranded Cable:
is a type of cable in which a number of wires enclosed in an outer jacket are used to transmit the electrical signal.

Sunshield:
is a movable accessory placed on top of outdoor housings to prevent direct light falling on the camera.

Switcher:
A device to switch between several cameras to one monitor. Switchers can be active or passive and can some be set up to automatically switch to a camera in an area where an alarm trips.

Sync Generator:
is a device which generates sync pulses which are then used to synchronize cameras.

Synchronization:
is a process which ensures that the formation of frames in a multi camera system start at the same time. There are different ways to achieve camera synchronization.

Terminal Strip:
is a clamp used to secure the cables firmly to the housing base.

Test Pattern Generator:
is a device which generates a test pattern to be used to adjust and test the monitor.

Thermal Paper:
is a special type of paper used in video printers.

Time Based Switching:
is a feature in matrix switchers which allows various programmed camera sequences to be initiated at various times.

Time Lapse VCR:
is a type of video cassette recorder especially designed for CCTV requirements. It allows more recording time on a single video tape by not recording all the frames.

Time/date Generator:
is a device which generates time and a date superimposes it on the video signal.

Touch Screen:
is a type of modern monitor screen. Action can be initiated by touching the relevant point on the monitor screen.

Trapezoidal Distortion:
is a type of distortion in the monitor caused due to non uniform scanning which makes the scanning lines look wider at the top than at the bottom of the monitor.

Tri-axial Cable:
is a type of co axial cable which has two layers of shield to provide better protection against EMI.

Twisted Pair Cable:
is a type of balanced cable in which a pair of cables are twisted and the signal is divided between them.

Two Speed Recorder:
is a type of domestic use VCR which has two speeds of recording/playback, standard and long play. The long play mode doubles the recording time of a standard tape.

Ultraviolet:
is electromagnetic radiation with a wavelength of less than 400 nm and is not visible to the human eye.

Unbalanced Cable:
is a type of cable in which the ends of the shields are grounded to different equipment with possibly varying ground potential. This unbalanced set up can give rise to ground loop currents and EMI induction.

UPS Un-interruptible Power Supply:
stores electricity and supplies power to a CCTV system during a power failure.

Usable video:
is the minimum video signal specified in the camera data sheet to generate an acceptable picture on the monitor. It is usually measured as a percentage of the full video.

EXAMPLE:  30% usable video=30% of 0.7 volts (full video or maximum video amplitude) = 0.2 volts.

Video Head:
is an internal part of a VCR which rotates very rapidly and writes the video signal on to the video tape during recording while reading the video signal from the tape during playback.

Vertical Resolution:
is the number of horizontal lines which can be resolved in a picture. It is limited by the television scanning method - NTSC, PAL etc.

Vertical Shift Register:
is a part of the interline transfer CCD chip and is placed in between every column of pixels. At the end of each frame the charge from the pixels are sent to the vertical shift register (VSR) and then row by row to the horizontal shift register.

Vertical Streaking:
is a type of picture distortion that occurs due to overloading of the pixels in an interline transfer chip. It appears as vertical streaks above and below the bright part of the picture.

VHS Victor Home System:
is a type of popular recording format used in video cassette recorders. The other type of formats are beta-max, 8mm, system 2000 and U-matrix (professional).

Vibration Sensor:
is a type of device which can be activated by vibrations in a pre determined zone and can be interfaced with a switcher to switch the nominated camera for extended viewing.

Video Amplifier:
is a type of amplifier used to boost the strength of a video signal.

Video Cassette Recorder:
is a device which can record (or playback) video and audio signals on a magnetic tape housed in a cassette.

Video Distribution Amplifier:
is a type of amplifier used not only to boost the strength but also create multiple outputs of the video signal.

Video Intercom:
is a door entry system which uses both audio and video to communicate and/or control movement of people.

Video Monitoring:
is a new trend which uses video to monitor remote sites in any part of the world. The video images are transmitted through the telephone network.

Video Motion Detector:
is a device which can detect unwanted movement in the picture and then generate an alarm.

Wave Length:
is the distance traveled by an electro magnetic wave during one cycle.

White Level:
The brightest part of a video signal corresponding to approximately 1.0 volt.

Wide Angle Lens:
is a type of lens which gives a wide view of the scene and has a magnification ratio of less than 1.

Zoom Ratio:
is the ratio between the maximum and minimum focal length of a zoom lens.

TERMS AND DEFINITIONS

AGC

Automatic Gain Control. A circuit for automatically controlling amplifier gain in order to maintain a constant output voltage with a varying input voltage within a predetermined range of input-to-output variation.

Aperture

In television optics, it is the effective diameter of the lens that controls the amount of light reaching the photoconductive or photoemitting image pickup sensor.

Aperture Correction

Compensation for the loss in sharpness of detail because of the finite dimensions of the image elements or the dot-pitch of the monitor.

Aspect Ratio

The ratio of width to height for the frame of the televised picture. 4:3 for standard systems, 5:4 for 1K x 1K, and 16:9 for HDTV.

Attenuation

In general terms, a reduction in signal strength.

Auto Balance

A system for detecting errors in color balance in white and black areas of the picture and automatically adjusting the white and black levels of both the red and blue signals as needed for correction.

Auto Light Range

The range of light, e.g., sunlight to moonlight, over which a TV camera is capable of automatically operating at specified output.

Automatic Brightness Control

In display devices, the self-acting mechanism which controls brightness of the device as a function of ambient light.

Automatic Frequency

An arrangement whereby the frequency of an oscillator is automatically maintained within specified limits.

Automatic Gain Control

A process by which gain is automatically adjusted as a function of input or other specified parameter.

Automatic Iris Lens

A lens that automatically adjusts the amount of light reaching the imager.

Automatic Light Control

The process by which the illumination incident upon the face of a pickup device is automatically adjusted as a function of scene brightness.

Back Porch

That portion of the composite picture signal which lies between the trailing edge of the horizontal sync pulse and the trailing edge of the corresponding blanking pulse.

Bandwidth

The number of cycles per second (Hertz) expressing the difference between the lower and upper limiting frequencies of a frequency band; also, the width of a band of frequencies.

Bar Test Pattern

Special test pattern for adjusting color TV receivers or color encoders. The upper portion consists of vertical bars of saturated colors and white. The power horizontal bars have black and white areas and I and Q signals.

Blooming

The defocusing of regions of the picture where the brightness is at an excessive level, due to enlargement of spot size and halation of the fluorescent screen of the cathode-ray picture tube. In a camera, sensor element saturation and excess which causes widening of the spatial representation of a spot light source.

Bounce

Sudden variations in picture presentation (brightness, size, etc.,) independent of scene illumination.

Brightness

The attribute of visual perception in accordance with which an area appear to emit more of less light. (Luminance is the recommended name for the photo-electric quantity which has also been called brightness.)

Broadband

In television system use, a device having a bandpass greater than the band of a single VHF television channel.

Burned-In-Image

Also called burn. An image which persists in a fixed position in the output signal of a camera tube after the camera has been turned to a different scene or, on a monitor screen.

CCD

See Charge Coupled Device

C Mount

A television camera lens mount of the 16 mm format, 1 inch in diameter with 32 threads per inch.

CCTV

Common abbreviation for Closed-Circuit Television.

Charge-Coupled Device

CCD. For imaging devices, a self-scanning semiconductor array that utilizes MOS technology, surface storage, and information transfer by shift register techniques.

Chroma

That quality of color which embraces both hue and saturation. White, black, and grays have no chroma.

Chroma Control

A control of color television receiver that regulates the saturation (vividness) of colors in a color picture.

Chroma Detector

Detects the absence of chrominance information in a color encoder input. The chroma detector automatically deletes the color burst from the color encoder output when the absence of chrominance is detected.

Chromatic Aberration

An optical defect of a lens which causes different colors or wave lengths of light to be focused at different distances from the lens. It is seen as color fringes or halos along edges and around every point in the image.

The color quality of light which is defined by the wavelength (hue) and saturation. Chromaticity defines all the qualities of color except its brightness.

Chrominance

A color term defining the hue and saturation of a color. Does not refer to brightness.

Chrominance Signal

That portion of the NTSC color television signal which contains the color information.

Clamp

A device which functions during the horizontal blanking or synchronizing interval to fix the level of the picture signal at some predetermined reference level at the beginning of each scanning line.

Clamping

The process that established a fixed level for the picture level at the beginning of each scanning line.

Clipping

The shearing off of the peaks of a signal. For a picture signal. This effects the positive (white).

Coaxial Cable

A particular type of cable capable of passing a wide range of frequencies with very low signal loss. Such a cable in its simplest form, consists of a hollow metallic shield with a single wire accurately placed along the center of the shield and isolated from the shield.

Color Burst

That portion of the composite color signal, comprising a few cycles of a sine wave of chrominance subcarrier frequency, which is used to establish a reference for demodulating the chrominance signal. Normally approximately 9 cycles of 3.579545 MHz.

Color Edging

Extraneous colors appearing at the edges of colored objects, and differing from the true colors in the object.

Color Encoder

A device which produces an NTSC color signal from separate R, G, and B video inputs.

Color Fringing

Spurious colors introduced into the picture by the change in position of the televised object from field to field.

Color Purity

The degree to which a color is free of white or any other color. In reference to the operation of a tri-color picture tube it refers to the production of pure red, green or blue illumination of the phosphor dot face plate.

Color Saturation

The degree to which a color is free of white light.

Color Sync Signal

A signal used to establish and to maintain the same color relationships that are transmitted.

Color Transmission

The transmission of a signal which represents both the brightness values and the color values in a picture.

Composite Video Signal

The combined picture signal, including vertical and horizontal blanking and synchronizing signals.

Compression

The reduction in gain at one level of a picture signal with respect to the gain at another level of the same signal.

Contrast

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

Contrast Range

The ratio between the whitest and blackest portions of television image.

Convergence

The crossover of the three electron beams of a three-gun tri-color picture tube. This normally occurs at the plane of the aperture mask.

Crosstalk

An undesired signal from a different channel interfering with the desired signal.

dB

Basically, a measure of the power ratio of two signals. In system use, a measure of the voltage ratio of two signals, provided they are measured across a common impedance.

Decoder

The circuitry in a color TV receiver which transforms the detected color signals into a form suitable to operate the color tube.

Definition

The fidelity of a television system to the original scene.

Depth of Field

The in-focus range of a lens or optical system. It is measured from the distance behind an object to the distance in front of the object when the viewing lens shows the object to be in focus.

Depth of Focus

The range of sensor-to-lens distance for which the image formed by the lens is clearly focused.

Digital Signal Processing

An algorithm within the camera that digitizes data (the image). Examples include automatic compensate for backlight interference, color balance variations and corrections related to aging of electrical components or lighting. Functions such as electronic pan and zoom, image annotation, compression of the video for network transmission, feature extraction and motion compensation can be easily and inexpensively added to the camera feature set.

Distortion

The deviation of the received signal waveform from that of the original transmitted waveform.

Distribution Amplifier

A device that provides several isolated outputs from one looping or bridging input, and has a sufficiently high input impedance and input-to-output isolation to prevent loading of the input source.

Dynamic Range

The difference between the maximum acceptable signal level and the minimum acceptable signal level.

EIA Sync

The signal used for the synchronizing of scanning specified in EIA Standards RS-170, RS-330, RS-343, or subsequent issues.

Equalizer

An electronic circuit that introduces compensation for frequency discriminative effects of elements within the television system, particularly long coaxial transmission systems.

Fiber Optics
        Also called optical fibers or optical fiber
        bundles.    An assemblage of transparent glass
        fibers all bundled together parallel to one another.
        The length of each fiber is much greater than its
        diameter. This bundle of fibers has the ability to
        transmit a picture from one of its surfaces to the
        other around curves and into otherwise
        inaccessible places with an extremely low loss of
        definition and light, by a process of total
        reflection.

Field

One of the two equal but vertically separated parts into which a television frame is divided in an interlaced system of scanning. A period of 1/60 second separates each field start time.

Field of View

The maximum angle of view that can be seen through a lens or optical instrument.

Focal Length

Of a lens, the distance from the focal point to the principal point of the lens.

Focal Plane

A plane (through the focal point) at right angles to the principal point of the lens.

Focal Point

The point at which a lens or mirror will focus parallel incident radiation.

Footcandle

See lumen/ft 2.

Footlambert (FL)

A unit of luminance equal to 1/candela per square foot or to the uniform luminance at a perfectly diffusing surface emitting or reflecting light at the rate of one lumen per square foot. A lumen per square foot is a unit of incident light and a footlambert is a unit of emitted or reflected light. For a perfectly reflecting and perfectly diffusing surface, the number of lumens per square foot is equal to the number of footlamberts.

Frame

The total area, occupied by the television picture, which is scanned while the picture signal is not blanked.

Frame Frequency

The number of times per second that the frame is scanned. The U.S. standard is 30 frames per second.

Frame Transfer

A CCD imager where an entire matrix of pixels is read into storage before being output from the camera. Differs from Interline Transfer where lines of pixels are output

Frequency Interlace

The method by which color and black and white sideband signals are interwoven within the same channel bandwidth.

Frequency Response

The range of band of frequencies to which a unit of electronic equipment will offer essentially the same characteristics.

Front Porch

The portion of a composite picture signal which lies between the leading edge of the horizontal blanking pulse and the leading edge of the corresponding sync pulse.

f/Stop

Also called F Number and F System. Refers to the speed or ability of a lens to pass light. It is calculated by dividing the focal length of the lens by its diameter.

Gain

An increase in voltage or power, usually expressed in dB.

Gamma

A numerical value, or the degree of contrast in a television picture, which is the exponent of that power law which is used to approximate the curve of output magnitude versus input magnitude over the region of interest.

Gamma Correction

To provide for a linear transfer characteristic from input to output device.

Genlock

A device used to lock the frequency of an internal sync generator to an external source.

Ghost

A spurious image resulting from an echo.

Gray Scale

Variations in value from white, through shades of gray, to black on a television screen. The gradations approximate the tonal values of the original image picked up by the TV camera.

Hue

Corresponds to colors such as red, blue, etcetera.

Hum

Electrical disturbance at the power supply frequency or harmonics thereof.

Image Intensifier

A device coupled by fiber optics to a TV image pickup sensor to increase sensitivity. Can be single or multi stage.

Image Plane

The plane at right angles to the optical axis at the image point.

Impedance (input or output)

The input or output characteristic of a system component that determines the type of transmission cable to be used. The cable used must have the same characteristic impedance as the component. Expressed in ohms. Video distribution has standardized on 75-ohm coaxial and 124-ohm balanced cable.

Incident Light

The light that falls directly on an object.

Insertion Loss

The signal strength loss when a piece of equipment is inserted into a line.

Interference

Extraneous energy which tends to interfere with the reception of the desired signals.

Interline Transfer

A technology of CCD design, where rows of pixels are output from the camera. The sensor's active pixel area and storage register are both contained within the active image area. This differs from "frame transfer" cameras that move all active pixels to a storage register outside of the active area.

Interlaced Scanning

A scanning process for reducing image flicker in which the distance from center to center of successively scanned lines is two or more times the nominal line width, and in which the adjacent lines belong to different fields.

Iris

An adjustable aperture built into a camera lens to permit control of the amount of light passing through the lens.

Isolation Amplifier

An amplifier with input circuitry and output circuitry designed to eliminate the effects of changes made at either upon the other.

Jitter

Small, rapid variations in a waveform due to mechanical disturbances or to changes in the characteristic of components. Supply voltages, imperfect synchronizing signals, circuits, etc.

Lens

A transparent optical component consisting of one or more pieces of optical glass with surfaces so curved (usually Spherical), that they serve to converge or diverge the transmitted rays of an object, thus forming a real or virtual image of that object.

Lens Preset Positioning

Follower Pots are installed on lens that allows feedback to the controller information relevant to zoom and focus positioning allowing the controller to quickly adjust to a preselected scene and arrive in focus at the proper focal length automatically.

Lens Speed

Refers to the ability of a lens to transmit light, represented as the ratio of the focal length to the diameter of the lens. A fast lens would be rated <f/1.4; a much slower lens might be designated as> f/8. The larger the f number, the slower the lens.

Light

Electromagnetic radiation detectable by the eye, ranging in wavelength from about 400 to 750 nm.

Line Amplifier

An amplifier for audio or video signals that feeds a transmission line; also called program amplifier.

Loop Through

Also called looping. The method of feeding a series of high impedance circuits (such as multiple monitor/displays in parallel) from a pulse or video source with a coax transmission line in such a manner that the line is bridged (with minimum length stubs) and that the last unit properly terminates the line in its characteristic impedance. This minimizes discontinuities or reflections on the transmission line.

Loss

A reduction in signal level or strength, usually expressed in dB. Power dissipation serving no useful purpose.

Low-Frequency Distortion

Distortion effects which occur at low frequencies. In television, generally considered as any frequency below the 15.75-kHz line frequency.

Lumen (LM)

The unit of luminous flux. It is equal to the flux through a unit solid angle (steradian) from a uniform point source of one candela or to the flux on a unit surface of which all points are at a unit distance from a uniform point source of one candela.

Lumen/FT2

A unit of incident light. It is the illumination on a surface one square foot in area on which a flux of one lumen is uniformly distributed, or the illumination at a surface all points of which are at a distance of one foot from a uniform source of one candela.

Luminance

Luminous intensity (photometric brightness) of any surface in a given direction per unit of projected area of the surface as viewed from that direction, measured in footlamberts (fl).

Luminance Signal

That portion of the NTSC color television signal which contains the luminance or brightness information.

Lux

International System (Sl) unit of illumination in which the meter is the unit of length. One lux equals one lumen per square meter.

Matrix Switcher

A combination or array of electromechanical or electronic switches which route a number of signal sources to one or more designations.

Modulation

The process, or results of the process, whereby some characteristic of one signal is varied in accordance with another signal. The modulated signal is called the carrier. The carrier may be modulated in three fundamental ways: by varying the amplitude, called amplitude modulation; by varying the frequency, called frequency modulation; by varying the phase, called phase modulation.

Monitor

A unit of equipment that displays on the face of a picture tube the images detected and transmitted by a television camera.

Monochrome

Black and white with all shades of gray.

Monochrome Signal

In monochrome television, a signal wave for controlling the brightness values in the picture. In color television, that part of the signal wave which has major control of the brightness values of the picture, whether displayed in color or in monochrome.

Monochrome Transmission

The transmission of a signal wave which represents the brightness values in the picture, but not the color (chrominance) values.

ND Filter

A filter that attenuates light evenly over the visible light spectrum. It reduces the light entering a lens, thus forcing the iris to open to its maximum.

Noise

The word "noise" originated in audio practice and refers to random spurts of electrical energy or interference. In some cases, it will produce a "salt-and-pepper" pattern over the televised picture. Heavy noise is sometimes referred to as "snow".

Non-Composite Video

A video signal containing all information except sync.

NTSC

Abbreviation for National Television Systems Committee. A committee that worked with the FCC in formulating standards for the present day United States color television system.

Output

The signal level at the output of an amplifier or other device.

Pan and Tilt

A device upon which a camera can be mounted that allows movement in both the azimuth (pan) and in the vertical plane (tilt).

Pan/Tilt Preset Positioning

Follower pots are installed on pan/tilt unit to allow feedback to the controller and provides information relevant to horizontal and vertical positioning, allowing the controller to quickly adjust to a pre-selected scene automatically.

Patch Panel

A panel where circuits are terminated and facilities provided for interconnecting between circuits by means of jacks and plugs.

Peak Pulse Amplitude

The maximum absolute peak value of a pulse, excluding those portions considered to be unwanted, such as spikes.

Peak-to-Peak

The amplitude (voltage) difference between the most positive and the most negative excursions (peaks) of an electrical signal. A full video signal measures one volt peak to peak.

Picture Element

See Pixel

Pixel

Short for Picture Element. A pixel is the smallest area of a television picture capable of being delineated by an electrical signal passed through the system of part thereof. The number of picture elements (pixels) in a complete picture, and their geometric characteristics of vertical height and horizontal width, provide information on the total amount of detail which the raster can display and on the sharpness of the detail, respectively.

Primary Colors

Three colors wherein no mixture of any two can produce the third. In color television these are the additive primary colors red, blue and green.

Progressive Scan

The progressive scan format outputs data from the camera (the signal) in sequential order as it is scanned. The scan format produces a full frame of video in a continuous stream, rather than half the image per output sequence in traditional RS-170 CCD cameras. Standard RS-170 video is interlaced and output in two separate fields, generating essentially half the image at a time. With Cohu's new 6600 Series Progressive Scan Camera, a new, full image is output from the camera every 1/60th second, making it ideal for machines to more quickly process and display information, or act according to programmed instructions.

Resolution (horizontal)

The amount of resolvable detail in the horizontal direction in a picture. It is usually expressed as the number of distinct vertical lines, alternately black and white, which can be seen in a distance equal to picture height.

Resolution, Limiting

The details that can be distinguished on the television screen. Vertical resolution refers to the number of horizontal black and white lines that can be resolved in the picture height. Horizontal resolution refers to the black and white lines resolved in a dimension equal to the vertical height and may be limited by the video amplifier bandwidth.

Resolution (vertical)

The amount of resolvable detail in the vertical direction in a picture. It is usually expressed as the number of distinct horizontal lines, alternately black and white, which can theoretically be seen in a picture.

Retained Image

Also called image burn. A change produced in or on the target which remains for a large number of frames after the removal of a previously stationary light image and which yields a spurious electrical signal corresponding to that light image.

RF (Radio Frequency)

A frequency at which coherent electromagnetic radiation of energy is useful for communication purposes. Also, the entire range of such frequencies.

Ripple

Amplitude variations in the output voltage of a power supply caused by insufficient filtering.

Roll

A loss of vertical synchronization which causes the picture to move up or down on a receiver or monitor.

Saturation

In color, the degree to which a color is diluted with white light or is pure. The vividness of a color, described by such terms as bright, deep, pastel, pale, etc. Saturation is directly related to the amplitude of the chrominance signal.

Scanning

The process of moving the electron beam of a pickup tube or a picture tube across the target or screen area of a tube.

Sensitivity

In television, a factor expressing the incident illumination upon a specified scene required to produce a specified picture signal at the output terminals of a television camera.

Shutter

Ability to control the integration (of light) time to the sensor to less than 1/60 second; e.g: stop motion of moving traffic.

Signal-to-Noise Ratio

The ratio between useful television signal and disturbing noise or snow.

Snow

Heavy random noise.

Spike

A transient of short duration, comprising part of a pulse, during which the amplitude considerably exceeds the average amplitude of the pulse.

Standard Minimum Signal

1000 micro volts at 75 ohms (0dB mV) in RF systems; 0.7-VPP non-composite, 1-VPP composite in video systems.

Sync

A contraction of "synchronous" or "synchronize".

Sync Generator

A device for generating a synchronizing signal.

Sync Level

The level of the peaks of the synchronizing signal.

Sync Signal

The signal employed for the synchronizing of scanning.

Synchronizing

Maintaining two or more scanning processes in phase.

Tearing

A term used to describe a picture condition in which groups of horizontal lines are displaced in an irregular manner.

Test Pattern

A chart especially prepared for checking overall performance of a television system. It contains various combinations of lines and geometric shapes. The camera is focused on the chart, and the pattern is viewed at the monitor for fidelity.

Transients

Signals which exist for a brief period of time prior to the attainment of a steady-state condition. These may include overshoots, damped sinusoidal waves, etc.

Vertical Resolution

The number of horizontal lines that can be seen in the reproduced image of a television pattern.

Video Amplifier

A wideband amplifier used for passing picture signals.

Video Band

The frequency band width utilized to transmit a composite video signal.

Video Signal (Non-Composite)

The picture signal. A signal containing visual information and horizontal and vertical blanking (see also Composite Video Signal) but not sync.

Y Signal

A signal transmitted in color television containing brightness information. This signal produces a black and white picture on a standard monochrome receiver. In a color picture it supplies fine detail and brightness information.

Zoom

To enlarge or reduce, on a continuously variable basis, the size of a televised image primarily by varying lens focal length.

Zoom Lens

An optical system of continuously variable focal length, the focal plane remaining in a fixed position.

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Last modified: August 09, 2001