Video & Audio Terminology

3.58 MHz 
The approximate frequency of the subcarrier used in NTSC video to carry the color information. The actual frequency is 3.579545 MHz + 10 Hz.

Video format used by H.263 with 1408 by 1152 pixels.

Video format used by H.263 with 702 by 576 pixels.

4.43 MHz 
The approximate frequency of the subcarrier used in PAL video to carry the color information. The actual frequency is 4.43361875 MHz + 5 Hz.

A commonly used term for a component digital video format. The details of the format are specified in the CCIR (ITU-R) 601 standard document. The numerals 4:2:2 denote the approximate ratio of the sampling frequencies of the single luminance channel to the two color (chrominance) channels. For every four luminance samples, there are two samples of each color channel.

Same as 4:2:2 but with the addition of a key channel which is sampled four times for every four samples of the luminance channel.

Similar to 4:2:2 except that for every four luminance samples, the color channels are also sampled four times.

Similar to 4:2:2:4 except that for every four luminance samples, the color and key channels are also sampled four times.

ITU-R 601 (formerly CCIR) designates a "raw" digital video format with 704 x 480 pixels. 
A-B roll 
Videotape editing arrangement where scenes on tape are played alternately on VTRs A and B and recorded on VTR C. Typically, the final output recorded on CTR C contains some scenes from VTR A and some scenes from VTR B with transitions (cuts, mixes, wipes, etc.) between the scenes.

Absorption loss 
In telecommunications, attenuation of the optical signal within the fiber optic transmission medium. Usually specified in terms of dB/km.

AC coupling 
A method of coupling one circuit to another through a capacitor or transformer so as to transmit the varying (ac) characteristics of the signal while blocking the static (dc) characteristics. In some GVG distribution amplifiers, when the ac coupling mode is selected, a feedback loop maintains the output signal at an average dc level of 0 volts regardless of APL (average picture level) or dc offset of the incoming signal.

Ac/Dc coupling 
May also be called simply dc coupling Coupling between circuits which accommodates the passing of both ac and dc signals.

Active video 
The portion of a video signal that contains picture information.

Able to adjust or react to a video condition or application, as an adaptive circuit. This term usually refers to filter circuits.

Analog-to-digital converter.

A/D converter 
Analog-to-digital converter.

Analog-to-digital converter (ADC, A/D, A-to-D) 
A circuit that uses digital sampling to convert an analog signal into a digital representation of that signal.

Audio Engineering Society.

Informal name for a digital audio standard established jointly by the AES and EBU organizations. The sampling frequencies for this standard varies depending on the format being used; the sampling frequency for D1 and D2 audio tracks is 48 kHz.

Audio follow video.

Automatic gain control. 
To broadcast a signal. 
Distortion in the video signal which may manifest itself in different ways, depending on the type of aliasing:
Spectral aliasing is caused by interference between two frequencies, such as the luminance and chrominance frequencies or thechrominance and field scanning frequencies. It appears as moire or herringbone patterns, straight lines that become wavy, or rainbow colors. 
Spatial aliasing is distortion that occurs because of limitations in physical resolution of the scanning process. It appears, for example, as straight diagonal lines that become stairstepped or jagged. 
Temporal aliasing is distortion resulting from information lost between line or field scans. It appears, for example, when a video camera is focused on a computer screen; the video output shows a flickering bar on the computer screen because of the lack of scan synchronization of the camera and the computer. 
The adjustment of components in a system for optimum performance.

All inputs hostile 
Measurement technique, particularly for crosstalk, using worst case conditions (typically, full chroma signal on all inputs other than the one under test).

All ones 
A digital signal consisting of data that contains all logical ones. In telecommunications, a test signal consisting of 11111.

A display symbol set consisting of the twenty-six letters of the alphabet and the digits 0 through 9.

Alternate mark inversion (AMI) 
In telecommunications, an encoding protocol where successive data 1's are transmitted as alternate, equal positive and negative pulses, and data 0's are sent as spaces, each of zero amplitude.

Amp (A) 
A connector manufacturer.

Ampere (A) 
Unit of measure of electrical current.

The magnitude of a signal in voltage or current. Frequently expressed in terms of peak, peak-to-peak, or RMS.

Amplitude modulation (AM) 
A method of imposing information on a carrier signal, such as a sine wave, by varying its amplitude.

An adjective describing any signal that varies continuously as opposed to a digital signal, which contains discrete levels. 
A system or device which operates primarily on analog signals.

Analog component 
Another name for component video, such as RGB or Y, R-Y, B-Y as opposed to digital component video.

Append mode 
In video devices capable of creating key frame effects, a mode that permits new key frames to be added to an existing key frame effect to make the effect longer.

Off-line storage of video/audio onto back-up tapes, floppy disks, optical disks, etc.

ASCII (American Standard Code for Information Interchange) 
A standard code used extensively in data transmissions, in which 128 letters, numerals, symbols, and special codes are each represented by a binary number.

Application specific integrated circuit. An integrated circuit designed for special rather than general applications.

Assemble edit (assemble mode) 
An editing mode that replaces all signals on the record tape (video, audio, control, and time code tracks) with new signals.

Assembly language 
A symbolic computer language in which a programmer can create prograrms that the computer's assembler program will translate into machine language for controlling the computer. Assembly language is a higher level language one step above machine language.

Lacking synchronization. In video, a signal is asynchronous when its timing differs from that of the system reference signal. A foreign video signal is asynchronous before it is treated by a local frame synchronizer.

Audio tape recorder.

Advanced Television Systems Committee (USA). A group whose charter is to develop voluntary national standards for high definition television.

The decrease in amplitude of a signal.

A circuit that provides reduction of the amplitude of an electrical signal without introducing appreciable phase or frequency distortion.

Audio sound 
An electrical signal that carries sound information.

Audio bridge 
In telecommunications, a device that mixes multiple audio inputs and feeds back composite audio to each stations, minus that station's input. Also known as a mix-minus audio system.

Audio crosspoint module 
Circuit board containing crosspoints for audio signal switching.

Audio distribution amplifier (audio DA) 
A device used to replicate an audio signal, typically providing 6 outputs, each of which is identical to the input signal.

Audio-follow-video (AFV) 
An operational mode in which audio and video switchers are tied together so that when the operator selects the video source, the audio simultaneously and automatically switches to the same source.

(Rear connector channel, motherboard.) The physical area, usually at the rear of an electronics frame, where modules and cables plug into the system.

Back porch 
The portion of a video signal that occurs during blanking from the end of horizontal sync to the beginning of active video. The blanking signal portion which lies between the trailing edge of a horizontal sync pulse and the trailing edge of the corresponding blanking pulse. Color burst is located on the back porch.

Backup supply 
A redundant power supply that takes over if the primary power supply fails.

A circuit having two sides (conductors) carrying voltages which are symmetrical around a common reference point, typically ground.

The complete range of frequencies over which a circuit or electronic system can function with minimal signal loss, typically less than 3 dB. The information carrying capability of a particular television channel. In PAL systems the bandwidth limits the maximum visible frequency to 5.5 MHz, in NTSC, 4.2 MHz. The CCIR (TIU-R) 601 luminance channel sampling frequency of 13.5 MHz was chosen to permit faithful digital representation of the PAL and NTSC luminance bandwidths without aliasing.

BCD (binary coded decimal) 
A coding system in which each decimal digit from 0 to 9 is represented by four binary (0 or 1) digits.

Informal name for Betacam, a professional color difference videotape recording format that uses the Y, R-Y, and B-Y color difference components. Also the name of a consumer videotape recording format that is completely different from the professional Betacam format.

Portable camera/recorder system using 1/2-inch tape originally developed by Sony. The name may also refer just to the recorder or the interconnect format; Betacam uses a version of the Y, R-Y, B-Y color difference signal set. Betacam is a registered trademark of the Sony Corporation.

Betacam SP 
A superior performance version of Betacam. SP uses metal particle tape and a wider bandwidth recording system.

Bit (binary digit) 
The smallest part of information in a binary notation system. A bit is a single one or zero. A group of bits, such as 8 bits or 16 bits, compose a byte. The number of bits in a byte depends upon the processing system being used. Typical byte sizes are 8, 16, and 32.

Bayonet Neill-Concelman. A cable connector used extensively in television named for its inventor.

A type of network circuit used to match circuits to each other, ensuring minimum transmission impairment. 
To place one circuit in parallel with another.

Having an essentially uniform response over a wide range of frequencies. 
Capable of handling frequencies greater than those required for high-grade voice communications (higher than 3 to 4 kilohertz).

A circuit or component which isolates one electrical circuit from another. 
A digital storage device used to compensate for a difference in the rate of flow of information or the time of occurrence of events when transmitting information from onedevice to another. 
In telecommunications, a protective material used in cabling optical fiber to cover and protect the fiber. The buffer material has no optical function.

A central conductor for the primary signal path. A signal path to which a number of inputs may be connected for feed to one or more outputs.

Button per source 
A control panel which has a separate button for each source. Also called button per function.

Bypass relay 
A relay used to bypass the normal electrical route in the event of power, signal, or equipment failure.

Bypass switcher 
An audio-follow-video switcher usually associated with a master control switcher. Used to bypass the master control switcher output during emergencies, failures, or off-line maintenance.

A group of data bits which are processed together. Typically, a byte consists of 8, 16, or 32 bits.

A device that stores electrical energy. It allows the apparent flow of alternating current while blocking the flow of direct current. The degree to which it allows ac flow depends on the frequency of the signal and the size of the capacitor. Capacitors are used in filters, delay-line components, couplers, frequency selectors, timing elements, voltage transient suppression, etc.

Cathode ray tube (CRT) 
A tube, usually glass, which is narrow at one end and widens at the other to create a surface onto which pictures can be projected. The narrow end contains circuits to generate and focus an electron beam on the luminescent screen at the other end. Used to display pictures in TV receivers, video monitors, oscilloscopes, computers, etc.

A digital effects processing path for video. 
A particular signal path. 
A portion of the television broadcast spectrum assigned to a particular broadcasting station.

Character generator (CG) 
A computer used to generate text and sometimes graphics for video titles.

Informal term meaning integrated circuit.

That portion of the video signal which contains the color information (hue and saturation). Video picture information contains two components: luminance (brightness and contrast) and chrominance (hue and saturation).

CIF (Common Interchange Format) 
352x288 pixels; often used for H.261 and H.263 video codecs. 
The interconnection of a number of devices to perform an electronic function. 
Clamp, clamping 
The circuit or process that restores the dc component of a signal. A video clamp circuit, usually triggered by horizontal synchronizing pulses, re-establishes a fixed dc reference level for the video signal. Some clamp circuits clamp sync tip to a fixed level, and others clamp back porch (blanking) to a fixed level. A major benefit of a clarnp is the removal of low-frequency interference, especially power-line hum. 
Coaxial cable 
A cable which has a metallic noise shield surrounding a signal-carrying conductor. In television, the cable impedance is 75 ohms. 
Color bars 
A video test signal widely used for system and monitor setup. Contains bands of color with fixed amplitudes and saturations. 
Common mode rejection (CMR) 
A measure of how well a differential amplifier rejects a signal which appears simultaneously and in-phase at both input terminals. As a specification, CMR is usually stated as a dB ratio at a given frequency. 
Common mode rejection ratio 
For a differential amplifier, the ratio of differential gain to common mode gain. 
Expressed in dB, the ratio of common mode input voltage to output voltage. 
For an operational amplifier, the ratio of the change in input/offset voltage to the change in common mode voltage. 
Composite sync (CS) 
A video synchronizing signal that contains horizontal and vertical synchronizing information. Often referred to simply as sync. 
Composite video 
An encoded video signal, such as NTSC or PAL video, that includes horizontal and vertical synchronizing information. 
A digital picture manipulator effect where the picture is made proportionally smaller. 
Improper video signal level caused by nonlinearity in a circuit's transfer function. Results in lack of detail in either the black or white areas of the video picture. Can also be caused by pointing a video camera at a scene that has a total black-to-white range. Wider than a standard television signal can handle. 
The manner in which two circuits or systems are connected. Usually this involves either ac or dc coupling. 
An electronic switch, usually part of an array of switches, that allows video or audio to pass when the switch is closed. 
Undesired transmission of signals from one circuit into another circuit in the same system. Usually caused by unintentional capacitive (ac) coupling. 
Signal interference from one part of a videotape to another. 
A component digital videotape recording format that conforms to the specifications set in the CCIR (ITU-R) 601 standard. 
An 8-bit composite digital videotape recording format in which the composite video signal is digitized by sampling it at the rate of four times the frequency of subcarrier (4fsc). The 4fsc frequency in NTSC is 14.3 MHz and 17.7 MHz in PAL. 
An unofficial term for a composite digital videotape recording format invented by Panasonic.

D/A converter (digital to analog) 
A device that converts digital signals to analog signals.

Data compression 
A technique that provides for the transmission or storage, without noticeable information loss, of few data bits than were originally used when the data was created.

dB (decibel) 
A measure of voltage, current, or power gain equal to l/10 of a Bel. Given by the equations 20 log Vout/Vin, 20 log Iout/In, or 10 log Pout/Pin.

A measure of power relative to 1 mW. 0 dBm equals 1 mW.

D connector 
A type of connector that has a trapezoidal shell resembling a "D."

Dc offset 
The amount that the dc component of the signal has shifted from its correct level.

The time required for a signal to pass through a device or conductor.

A circuit that demodulates or decodes the desired signal from amplitude and/or frequency modulation present on a carrier wave.

Demultiplexer (demux) 
A device used to separate two or more signals that were previously combined by a compatible multiplexer and are transmitted over a single channel.

Differential dc 
Maximum dc voltage that can be applied between the differential inputs of an amplifier while maintaining linear operation.

Differential gain 
A change in subcarrier 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 looping input 
A video input port that allows the signal to be looped through to another input.

Circuitry in which data carrying signals are restricted to either of two voltage levels, corresponding to logic 1 or 0. A circuit which has two stable states: high or low, on or off.

DIP switch 
Dual in-line package switch. A PC module mounted switch package of dual inline style, typically mounting from two to eight switches and used in such functions as mode assignment and address selection.

Distribution amplifier (DA) 
A device used to replicate an input signal, typically providing 6 outputs, each of which is identical to the input. May also include delay and/or cable equalization capabilities.

Edit suite 
Room where editing is done.

Production of finished videotape from source tape. Editing usually involves the use of a computer editing system to select scenes and audio from multiple video and audio sources and record them into a finished program on a single videotape.

An editing system operator. Also the informal term used for an edit controller.

Editor interface 
A serial communications link between an edit controller and peripheral devices, such as a video switcher and tape machines. The editor interface allows the edit controller to send control commands to the peripherals and receive status reports from the peripherals.

Electrically erasable programmable read-only memory. A type of memory chip that can hold data even when power is removed. The memory can be erased electronically so that new data can be stored.

Erasable programmable read-only memory. A type of memory chip that can hold data even when power is removed. The memory can be erased (usually by ultraviolet light exposure) so that new data can be stored.

Equalization (EQ) 
Process of altering the frequency response of a video amplifier to compensate for high-frequency losses in coaxial cable. 
In audio, to improve the sound quality by increasing or decreasing the gain of the signal at various frequencies.

Fall time 
The length of time during which a pulse decreases from 90 to 10 percent of its maximum amplitude.

Fan-out (fanout) (noun) 
The number of parallel loads within a given IC logic family that can be driven by a single output of a logic device.

A television signal source.

Fiber bundle 
A group of parallel optic fibers contained within a common jacket. A bundle may contain from just a few to several hundred fibers.

Fiber optics 
Use of optical cable to transmit images or signals in the form of light around corners and over distances with extremely low losses.

First generation 
The first copy of a videotape. A copy of that copy is termed second generation.

A video transition where the sources selected ton the program and preset buses exchange places at the end of the transition. 
A digital logic circuit whose output follows the signal present on the input at the time that a clock signal occurs.

In television, the specific form of the signals that make up the video signal. For example, component versus composite format. 
To prepare or preprogram a storage medium, such as a floppy disk, so that it can receive and store data.

A complete video picture composed of two fields (two complete interlaced scans of the monitor screen). A frame consists of 525 interlaced horizontal lines of picture information in NTSC, 625 in PAL. 
A metal cabinet (also known as a tray) which holds circuit boards.

In digital picture manipulators, the ability to stop or hold a frame of video so that the picture is frozen like a snapshot.

Freeze frame 
The storing of a single frame of video.

The number of complete cycles of a periodic waveform that occur in a given length of time. Usually specified in cycles per second (Hertz).

Frequency Modulation (FM) 
Modulation of a sine wave or "carrier" by varying its frequency in accordance with amplitude variations of the modulating signals.

Frequency response 
A measure of how effectively a circuit or device passes signals or different frequencies applied to it.

Front porch 
The blanking signal portion which lies between the end of the active picture information and the leading edge of horizontal sync.


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

A signal used to trigger the passage of other signals through a circuit. 
A digital logic device whose output state depends on the states of the logic signals presented to its inputs.

Gate array 
A set of basic logic gates contained in one integrated circuit.

GRB (green, red & blue; RGB) 
The three primary colors used in video processing, often referring to the three unencoded outputs of a color camera. The sequence of GBR indicates the mechanical sequence of the connectors in the SMPTE standard.

General purpose interface (GPI) 
A parallel interconnection scheme that allows remove control of certain functions of a device. One wire per function. 
May also refer to any nonspecific interface between equipment. Usually refers to a serial connection (RS232 or RS422 format) between computer modules.

Gen-lock (genlock) 
To phase-lock the timing of one piece of equipment to another.

Gen-lockable master 
A main facility sync pulse generator that is capable of locking to an outside source of video.

One of the three primary color signals (red, green, and blue) produced by cameras and other video sources.

H (Horizontal) 
In television signals, may refer to any of the following: 
The horizontal period or rate. 
The horizontal line of video information. 
The horizontal sync pulse.

H & V lock time 
The length of time it takes for a device to lock to horizontal and vertical sync.

Hard disk 
A digital data storage device using a rigid, magnetic disk.

Hard white clip 
Stops the composite video going above a predetermined level.

A periodic wave having a frequency that is an integral multiple of the fundamental frequency. For example, a wave with twice the frequency of the fundamental frequency is called the second harmonic.

Harmonic distortion 
The production of harmonics at the output of a circuit when period wave is applied to its input. The level of the distortion is usually expressed as a percentage of the level of the input.

High-definition television.

High frequency (HF) 
The frequency bands from 3 to 30 MHz.

High frequency loss 
Loss of signal amplitude at higher frequencies, caused for example, by passing a signal through a coaxial cable.

High-Z looping input 
A high-impedance input circuit which also includes an output to enable routing the signal to another piece of equipment.

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.

A circuit (often a coil) that introduces a small amount of voltage at power-line frequency into the video path to cancel unwanted ac hum.

Integrated circuit.


The total of the resistive and reactive opposition, measured in ohms, that a circuit presents to the flow of alternating current at a given frequency.

Input selector 
A routing switcher or auxiliary bus used to expand the number of video or key inputs that can feed an input of a digital picture manipulator or keyer. Many keyers only accept one key source and fill, but by connecting an input selector to those inputs, many more source and fill signals become available just by selecting crosspoints on the input selector.

A device's input loops back out so that the incoming signal can be sent elsewhere.

Integrated circuit 
An electronic device in which both active and passive circuits are contained in a single miniature multi-pin package.

Intensity modulation (IM) 
Used in fiber optics as a method of transmission in which the analog signal directly modulates the light source.

Input/output. Typically refers to sending information or data signals to and from devices.

A socket or receptacle into which a mating plug is inserted in order to make an electrical connection.

Also called key source or key cut. A signal that can be used to electronically "cut a hole" in a video picture to allow for insertion of other elements such as text or another video image. The key signal is a switching or gating signal for controlling a video mixer which switches or mixes between the background video and the inserted element. 
The composite effect created by cutting a hole in one image and inserting another image into the hole.

Key bus 
A video switcher crosspoint bus used to select key sources (hole cutters) and/or key fills. Signals available to the key bus are typically the same sources and fills that are supplied to the other switcher crosspoint buses plus additional external key sources and fills.

Key channel 
A channel of a digital picture manipulator that is used for manipulating key signals while the corresponding key fill video is manipulated by another channel.

An electronic circuit that creates a control signal to control a video multiplier based on selective information contained in a video signal.

Key frame (keyframe) 
An effect that has been stored in memory, similar to a snapshot photograph. Individual key frames can be strung together to create an overall key frame effect, which is similar to animation.

Key frame effect 
An overall effect consisting of a series of snapshots called key frames. When the key frames are replayed, the machine (switcher, DPM, etc.) automatically and gradually dissolves from one key frame to the next. A process called inbetweening defines what happens between key frames. The result is a moving animation effect.

Local area network.

Light-emitting diode.

The clear plastic cover on a pushbutton. 
The focusing mechanism of a camera.

The intensity of an electrical signal. 
In routing switchers, an independently controllable stratum of signals within a routing switcher. Typically, a routing switcher will have a level of video and one or more audio levels. 
A mix/effects (M/E) section of a video production switcher.

Lever arm (fader arm) 
Typically a "T" shaped handle that is used for manual video transitions on a production switcher. Moving the lever arm between two limits of an arc creates a change in voltage or digital data that is used to control the transition.

Line voltage 
The voltage level of the main power source to a device.

Log time 
That time at which a new source is placed on the program bus, usually recorded in the station log for FCC accounting and customer billing purpose.

Loop-through (loop-thru, looping) 
A type of video input circuit that provides two or more input connectors. One connector accepts the video input signal for use within the device in question, and the other connector provides a tap off of the input for routing the input signal to another piece of equipment.

The measurable, luminous intensity of a video signal. Differentiated from brightness in that the latter is nonrneasurable and sensory. The color video picture information contains two components: luminance (brightness and contrast) and chrominance (hue and saturation). The photometric quantity of light radiation.

A component video format invented by Panasonic for use in videotape recorders. The signal set consists of separate Y, I, and Q signals. The M refers to the way in which the tape is routed through the recording mechanism.

MII Format 
A second-generation component video format invented by Panasonic for use in videotape recorders. The signal set consists of separate Y, scaled R-Y, and scaled B-Y signals. The M refers to the way in which the tape is routed through the recording mechanism.

Multiplex analog components.

An AppleTMbrand computer used in desktop video production.

A function that provides a one-key stroke streamlined operation in place of a procedure having many keystrokes.

In a digital picture manipulator, the various processes used to alter a video image, such as transformations and programmed effects.

Master control system 
The switching link for video and audio sources used between a television facility and a transmitting device.

In editing, the process in which one or more VTRs (slaves) are controlled by another VTR (master). 
In sync generators, the process in which several sync generators (slaves) are controlled by one main sync generator (master).

In editing, a command that calculates the match frame for the time specified in the R-VTR's mark table IN column.

A logical network configured in a rectangular array of intersections of input-output leads. In routing switchers, a signal switching frame configured such that any frame input may be selected at any frame output. In a color television set or an encoded chroma keyer, the section that combines the luminance and color signals and transforms them into individual red, green, and blue signals. In the TV set, these signals are then applied to the picture-tube grids. In the encoded chroma keyer, these signals are used to generate a chroma key.

Megabits per second. Digital transmission speed in millions of bits per second.


One million bytes (actually 220 or 1,048,576); one thousand kilobytes.

Megahertz (MHz) 
One million hertz.

An IC package incorporating logic, memory, control, computer and/or interface circuits.

Mix (dissolve, crossfade) 
A transition between two video signals in which one signal is faded down as the other is faded up.

Mix/Effects (M/E) 
A subsystem of a video production switcher where a composite of two or more images can be created. Each M/E typically includes crosspoint buses, keyer(s), and mixer.

European term for production switcher. Complete term is vision mixer. 
A circuit which can mix two or more video signals. 
An audio console for combining audio sources.

A device that transforms a typical two-level computer signal into a form suitable for transmission over a telephone line. Also does the reverse-transforms an encoded signal on a telephone line into a two-level computer signal. Model is an acronym for modulator/demodulator.

A circuit that modifies a carrier wave by amplitude, phase, and/or frequency.

A printed circuit board or assembly that contains electronic components and slides into a cell.

In video, a device that directly displays a video picture from a camera, videotape recorder, or special-effects generator. 
A verb meaning to watch or listen to a signal.

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

A single slice of silicon substrate on which an integrated circuit is built. 
Elements or circuits formed within a single semiconductor substance.

A circuit board that accommodates plug-in cards or daughterboards and makes interconnections between them. May also provide cable input/output connections.

A computer operating system developed by Microsoft for IBM personal computers.

Multimode effect 
An effect that results from the difference in time required for different light signals to traverse the length of a multimode optical fiber.

Multimode fiber 
An optical fiber with a relatively large core diameter anywhere in between 25 and 200 microns in which more than one mode of light propagation takes place.

In switchers, the duplication of wipe patterns. Instead of one pattern, multiple patterns all of the same shape appear or screen. 
Signal mixing that takes place within a multiplier circuit.

The affiliation of television or radio stations such as ABC, CBS, NBC, CBC, BBC, etc. 
A combination of electrical elements, such as a group of interconnected computers.

Unwanted disturbance within an electronic system. Interference present in a video picture.

A memory system whose stored data is undisturbed by removal of operating power.

NTSC (National Television Systems Committee) 
Organization that formulated standards for the NTSC television system. Now describes the American system of color telecasting which is used mainly in North America, Japan, and parts of South America. NTSC television uses a 3.579545 MHz subcarrier whose phase varies with the instantaneous hue of the televised color and whose amplitude varies with the instantaneous saturation of the color. NTSC employs 525 lines per frame and 59.94 fields per second.

Signals that are not currently going out to broadcast or videotape recording. 
Signals received "out of the air" from a transmitter. To record signals off the air.

Not in use. Inactive.

Off-line editing 
Editing that is done using inexpensive, non-broadcast-quality equipment to produce an Edit Decision List (EDL) which will be used later for assembling a broadcast quality program using more expensive, high quality equipment.

The video signal in question is being broadcasted or videotaped. In Kaleidoscope, a portion of a channel's picture is on screen or its output is being combined with another digital effects processor to create the final video output.

On-edge switching 
A digital picture manipulator term meaning to switch input crosspoints (video sources) when the back (hidden) side of a double-sided transformed image rotates to the front and the front (visible) side rotates to the back. The switching occurs at the moment when only the edge of the image is visible.

An electronic device that generates alternating-current at a frequency determined by the values of the components in its circuits.

The current, voltage, power, or driving force delivered by a circuit or device.

Output impedance 
The impedance a device presents to its load. The impedance measured at the output terminals of a transducer with the load disconnected and all impressed driving forces taken as zero.

Output return loss 
A measure of the accuracy of the impedance match between a signal source (such as a cable) and its terminating load. An unequal impedance match causes some of the power from the source to be reflected back to the source, resulting in signal distortion. The ratio of the signal voltage at the load to that voltage reflected back to the source is defined as the return loss. This ratio is generally expressed in decibels (dB).

Output to output isolation 
The ratio of attenuation provided by the output stage to an interfering signal driving one output compared to a second output. The ratio is measured at the second output. A good specification protects output signals against incorrect cabling, such as accidental untermination or double termination.

PAL (phase alternate line) 
The name of the color television system in which the E'v component of burst is inverted in phase from one line to the next in order to minimize hue errors that may occur in color transmission. PAL-B (also called PAL-I) is a European color TV system featuring 625 lines per frame, 50 fields per second, and a 4.43361875 MHz subcarrier. It is used mainly in Europe, China, Malaysia, Australia, New Zealand, the Middle East, and parts of Africa. PAL-M is a Brazilian color TV system with phase alternation by line, but using 525 lines per frame, 60 fields per second, and a 3.57671149 MHz subcarrier.

Programmable array logic. An IC containing a large number of logic gates whose interconnections are programmable for specific applications.

Pretty amazing new services. Usually used jokingly for fancy telephony services.

Parallel data 
Transmission of data bits in groups along a collection of wires (called a bus). Analogous to the rows of a marching band passing a review point. A typical parallel bus may accommodate transmission of one 8-, 16-, or 32-bit byte at a time.

Parallel video mixer 
Video mixing architecture where two identical sets of multipliers are used to create a multilevel effect.

Parallel video processing 
A mixing architecture where the outputs of several video multipliers are summed to create a composite effect.

A method of verifying the accuracy of transmitted or recorded data. An extra bit appended to an array of data as an accuracy check during transmission. Parity may be even or add. For odd parity, if the number of 1's in the array is even, a 1 is added in the parity bit to make the total odd. For even parity, if the number of 1's in the array is odd, a 1 is added in the parity bit to make the total even. The receiving computer checks the parity bit and indicates a data error if the number of ones does not add up to the proper even or odd total.

In digital picture manipulators, the values of the field rate information produced by inbetweening two key frames. Visually, the path corresponds to the motion route that the image on the screen takes to move from one key frame to the next. May also include size changes, picture rotation, etc.

Printed circuit board. An insulating board onto which a circuit has been printed or etched.

The point of highest amplitude of a waveform or voltage.

Peak-to-peak (P-P) 
The amplitude (voltage) difference between the most positive and the most negative excursions (peaks) of an electrical signal. 
Phase (chroma phase, hue, tint)--The relative timing of a signal in relation to another signal. If the time for one cycle of a signal is represented as 360— along a time axis, the phase position for the second signal is called phase angle expressed in degrees. The subcarrier phase of TV colors can be adjusted, and this changes the hue of the colors themselves.

Phase inversion 
The condition whereby the output of a circuit produces a wave of the same shape and frequency but 180 degrees out of phase with the input.

Phase lock 
The phase of a signal follows exactly the phase of a reference signal.

Phase Locked Loop (PLL) 
A circuit containing an oscillator whose output phase or frequency locks onto and tracks the phase or frequency of a reference input signal. To produce the locked condition, the circuit detects any phase difference between the two signals and generates a correction voltage that is applied to the oscillator to adjust its phase or frequency.

Adjusting the delay of a video signal to match a reference video signal. This includes horizontal and subcarrier timing.

The smallest distinguishable and resolvable area in a video image. A single point on the screen. In digital video, a single sample of the picture. Derived from the words picture element.

Post production 
The editing process after the video footage has been shot.

Potentiometer (pot) 
A resistor that has a variable contact so that a portion of the potential applied between its ends may be selected.

Plain old telephony service. Typically analog basic phone services; as opposed to ISDN or intelligent network services.

An amplifier that raises the gain of a low-level signal so that it may be further processed without appreciable degradation in the signal-to-noise ratio.

A specific amount of time allowed for tape machines to run prior to an edit in order to get them up to speed and synchronized for the edit. In preparation for the edit, tapes are cued to a point ahead of the edit point to provide a proper preroll. The amount of preroll required varies with each type of VTR.

Presentation switcher (master control switch) 
Another term for "master control switcher" used in Europe and some other countries outside the US. There are minor differences applicable to the specific area of use.

To select a video source in preparation for taking it to air. 
A source selected on the preset bus or the action of selecting a source on the preset bus.

Preset bus 
In video and audio switchers, a row of crosspoint pushbuttons used to select the video or audio input that will be placed on-air during the next background transition. Also called preset background bus.

Programmable read only memory. A ROM that can be prograrmmed by the equipment manufacturer (rather than the PROM manufacturer).

Pulse distribution amplifier (DA) 
A device used to replicate an input timing signal, typically providing 6 outputs, each of which is identical to the input signal. May also perform cable equalization or pulse regeneration.

Pulse level 
The voltage amplitude of a pulse.

QCIF (Quarter CIF) 
176x144 pixels; common H.261 and H.263 video resolution. 
An equipment rack. In video, a standard equipment rack is 19 inches (48.26 cm) wide at the front. Most video equipment is designed to fit into a standard rack.

Rack unit (RU) 
Unit of measure of vertical space in an equipment rack. One rack unit is equal to 1.75 inches (4.45 cm). The height of a GVG electronics frame is typically specified in rack units.

RAM (random access memory) 
A temporary, volatile memory into which data can be written or from which data can be read by specifying an address.

Read before write 
A feature of some videotape recorders that plays back the video or audio signal off of tape before it reaches the record heads, sends the signal to an external device for modification, and then applies the modified signal to the record heads so that it can be re-recorded onto the tape in its original position.

Real time 
Computation or processing done in the present to control physical events occurring in the present. For example, when a digital effects system operator moves a joystick and the video images on the monitor appear to move simultaneously, the computations required to make the images move are said to have occurred in real time.

An electromechanical device having electrical contacts that open or close when current is applied to the activating mechanism of the device.

To restore a device to its default or original state. To restore a counter or logic device to a known state, often a zero output.

Resistive load 
A load in which the voltage is in phase with the current.

A component made of a material (such as carbon) that has a specified resistance or opposition to the flow of electrical current.

Return loss 
A measure of the accuracy of the impedance match between a signal source (such as a cable) and its terminating load. An unequal impedance match causes some of the power from the source to be reflected back to the source, resulting in signal distortion. The ratio of the signal voltage at the load to that voltage reflected back to the source is defined as the return loss. This ratio is generally expressed in decibels (dB).

Radio frequency.

Radio frequency interference. Spurious electromagnetic energy that interferes with electronic equipment or broadcast signals.

A coaxial cable type often used in television.

RGB (red, green, & blue, GRB) 
The three primary colors used in video processing, often referring to the three unencoded outputs of a color camera or VTR.

Ribbon cable 
Flat cable with multiple parallel conductors that have been individually insulated.

Rise time 
Time required for a pulse edge to rise from 10% to 90% of the final value.

Root mean square. A measure of effective (as opposed to peak) voltage of an AC waveform. For a sine wave, it is .707 times the peak voltage. For any periodic waveform, it is the square root of the average of the squares of the values through one cycle.

Routing switcher 
An electronic device that routes a user-supplied signal (audio, video, etc.) from any input to any user-selected output. Inputs are called sources. Outputs are called destinations.

A SMPTE parallel component digital video standard.

A document prepared by the Electronics Industries Association describing recommended practices for NTSC color television signals in the United States.

A standard, single-ended (unbalanced) interconnection scheme for serial data communications.

In telecommunications, a transmission specification for NTSC video and audio.

A standard, balanced interconnection scheme for serial data communications.

Abbreviation of rack unit.

A designator used to name one of the color signals (red minus luminance) of a color difference video signal. The formula for deriving R-Y from the red, green, and blue component video signals is .70R - .59G - .11B.

The sending of a group of commands at the same time.

An orbiting space vehicle containing a set of transponders that retransmit television broadcast signals back to earth receivers. 
A TV station licensed to rebroadcast the programming of a parent station.

Satellite downlink 
The communications path from a satellite to its ground station.

Satellite uplink 
The communications path from a ground station to its satellite.

Saturation (chroma, chroma gain, color) 
The intensity of the colors in the active picture. The voltage levels of the colors. The degree by which the eye perceives a color as departing from a gray or white scale of the same brightness. A 100% saturated color does not contain any white; adding white reduces saturation. In NTSC and PAL video signals, the color saturation at any particular instant in the picture is conveyed by the corresponding instantaneous amplitude of the active video subcarrier. 
The point on the operational curve of an amplifier at which an increase in input amplitude will no longer result in an increase in amplitude at the output.

One sweep of the target area in a camera tube or of the screen in a picture tube.

A diagram of the electrical scheme of a circuit with components represented by graphic symbols.

Sequential couleur avec memoire (sequential color with memory). A color television system with 625 lines per frame and 50 fields per second, developed by France and the USSR. Color difference information is transmitted sequentially on alternate lines as an FM signal.

Time-sequential transmission of data along a single wire. Analogous to a railroad train, where each car (data bit) follows the other in single file.

Serial control panel 
A control panel separate from the switcher (for example, a routing switcher) that communicates with the switcher via a serial connection.

Serial digital 
Digital information that is transmitted in serial form. Often used informally to refer to serial digital television signals. Serial interface A digital communications interface in which data is transmitted and received sequentially along a single wire or pair of wires. Common serial interface standards are RS232 and RS422. 
SIF (standard interchanage format) 
320 x 240 pixels 
Signal generator 
A test oscillator that can be adjusted to provide a test signal at some desired frequency, voltage, modulation, and waveform.

SMPTE (Society of Motion Picture and Television Engineers) 
A professional organization that sets standards for American television. 
A color difference video format that uses a variation of the Y, R-Y signal set. 
A time code (see SMPTE time code).

SMPTE time code 
Time code that conforms to SMPTE standards. It consists of an eight-digit number specifying hours:minutes:seconds:frames. Each number identifies one frame on a videotape. SMPTE time code may be of either the drop-frame or non-drop frame type. In GVG editors, the SMPTE time code mode enables the editor to read either drop-frame or non-drop frame code from tape and perform calculations for either type (also called mixed time code).

Surface-mount technology. See "surface mount."

Video noise.

Signal-to-noise ratio. The SNR relates how much stronger a signal is than the background noise. Usually expressed in decibels (dB).

Synchronous optical network. A telecommunications standard.

Equipment that produces video, such as cameras, tape recorders, graphics, and character generators. 
In digital picture manipulators, the origin of picture information applied to the input of a digital effects processor. May consist of a video component and sometimes a key component.

Spectral bandwidth 
In telecommunications, the spectral bandwidth for single peak devices is the difference between the wavelengths at which the radiant intensity is 50% (or 3 dB) down from the maximum value.

A curve shape produced on a computer or video device by connecting dots or points at various intervals along the curve. In digital picture manipulators, each key frame becomes a point on a curve and the user can control how straight or curved the path of the transformed image is as it travels through the key frame points.

A square or rectangular-shaped periodic wave that alternately assumes two fixed values for equal lengths of time, the transition being negligible in comparison with the duration of each fixed value.

A room designed for recording or broadcasting.

Subcarrier (SC) 
In NTSC or PAL video, a continuous sine wave of extremely accurate frequency which constitutes a portion of the video signal. The subcarrier is phase modulated to carry picture hue information and amplitude modulated to carry color saturation information. The NTSC subcarrier frequency is 3.579545 MHz, and the PAL-I frequency is 4.43361875 MHz. A sample of the subcarrier, called color burst, is included in the video signal during horizontal blanking. Color burst serves as a phase reference against which the modulated subcarrier is compared in order to decode the color information.

A small circuit board that mounts on a larger module.

Video format for H.263 (required) and H.261 (optional) with 128 by 96 pixels.

Surface mount 
A method of mounting subminiature integrated circuits and other components directly on the surface of a printed circuit board. Permits greater component density on boards, making the electronic equipment smaller.

Switcher (production switcher) 
Device that allows transitions between different video pictures. May also contain special effects generators.

The portion of an encoded video signal that occurs during blanking and is used to synchronize the operation of cameras, monitors, and other equipment. Horizontal sync occurs within the blanking period in each horizontal scanning line, and vertical sync occurs within the vertical blanking period.

Sync generator (Sync pulse generator, SPG) 
Device that generates synchronizing pulses need by video source equipment to provide proper equipment or studio timing. Pulses typically produced by a sync generator include subcarrier, burst flag, sync, blanking, H & V drives, color frame identification, and color black.

In step or in phase, as applied to two or more devices. A system in which all events occur in a predetermined timed sequence.

Sync pulse 
Timing pulses added to a video signal to keep the entire video process synchronized in time.

A lamp which lights to indicate that the associated video source is in use. Typical locations of tally lamps are on the front of video cameras and in the crosspoint pushbuttons of video switchers. 
The acknowledgment returned to the control panel or terminal that an operation has been executed.

Tally relay 
A relay whose contacts close when an associated function is placed on-air. Tally relays are used in video switchers to provide the customer a way to light a camera tally lamp when the camera is placed on air at the switcher panel.

Time-base corrector

Electronically linked meeting, conducted among groups in separate geographic locations.

Terminal block 
An insulating base equipped with one more more terminal connectors.

Terminal equipment 
Equipment at an end of communication lines that send and/or receive certain signals for specific services. Some examples in television include sync pulse generators, processing amplifiers, and distribution amplifiers.

Test point 
Typically a post in a circuit that can be monitored to test a parameter of the circuit.

Test signal 
An electronic signal with standard characteristics used to test the capability of circuits.

Test signal generator 
Device that generates special television signals used for aligning television equipment.

Time-base corrector 
Device used to correct for time base errors and stabilize the timing of the video output from a tape machine.

Time code 
Timing code laid down on videotape to give each frame a unique number so as to ensure exact transitions during editing.

Time delay 
The time required for a signal to travel through a circuit.

Typically refers to a single-frequency audio signal used as a level setting reference.

A semiconductor electronic device having three electrodes and used for signal buffering, amplification, etc.

Twisted pair 
A cable composed of two small insulated conductor twisted together. Since both wires have nearly equal exposure to any interference, the differential noise is slight.

Universal asynchronous receiver/transmitter. An integrated circuit that interfaces a microprocessor to a serial I/O port.

Unity gain 
An amplifier or active circuit in which the output amplitude is the same as the input amplitude.

The earth station that transmits signals to a satellite for relay to another location on the ground.

A trademarked name that has become the generic description for a vector display unit which allows visual checking of the phase and amplitude of the color components of a video signal.

Vertical interval 
The portion of the video signal that occurs between the end of one field and the beginning of the next. During this time, the electron beams in the cameras and monitors are turned off (invisible) so that they can return from the bottom of the screen to the top to begin another scan.

Vertical sync pulse 
The synchronizing pulse at the end of each field which signals the start of vertical retrace.

An electrical signal that carries television picture information.

Video crosspoint module 
In video switchers, a circuit board containing video switching crosspoints.

Video gain (white level, white bar, reference white) 
The range of light-to-dark values of the image which 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 mixer 
European term for video production switcher.

Video monitor 
A high-quality television set (without RF circuits) that accepts video baseband inputs directly from a TV camera, videotape recorder, etc.

Video path 
The electronic path within the device that routes and processes the video signals. Video path length refers to the amount of time required for a signal to travel from input to output.

Video processing amplifier 
A device that stabilizes the composite video signal, regenerates the synchronizing signals, and allows other adjustments to the video signal parameters.

Video signal 
An electrical signal that includes all of the information present in the television picture together with the necessary synchronizing signals.

Video switcher (production switcher, video mixer) 
Device that accepts inputs from a variety of video sources and allows the operator to select a particular source to be sent to the switcher's output(s). May also include circuits for video mixing, wiping, keying, and other special effects.

Videotape recorder (video tape recorder, VTR) 
A device which permits audio and video signals to be recorded on magnetic tape.

Video to audio crosstalk 
A measurement, typically in dB, of the amount of unwanted video signal energy present in an audio signal.

Vertical interval reference. Reference signal inserted into the vertical interval of source video. This signal is used further down the video chain to verify parameters and to automatically adjust gains and phase.

Vision mixer 
European term for video production switcher.

Voltage regulator 
A circuit used for controlling and maintaining a voltage at a constant level.

VU meter 
Volume-unit meter, a type of meter used to indicate average audio amplitude.

A measure of electrical power. The power expended when I ampere of direct current flows through a resistance of I ohm. The unit of electric power required to do work at the rate of 1 joule per second. Calculated by multiplying volts times amperes.

The shape of an electromagnetic wave. A graphical representation of voltage or current in relation to time.

Waveform monitor 
A device used to examine the video signal and synchronizing pulses. An oscilloscope designed especially for viewing the waveform of a video signal.

A system of material designed to direct confined electromagnetic waves in a direction determined by its physical boundaries.

White peak 
The maximum excursion of the video signal in the white direction at the time of observation.

Video containing information or allowing information entry, keyed into the video monitor output for viewing on the monitor CRT. A window dub is a copy of a videotape with time code numbers keyed into the picture. 
A video test signal consisting of a pulse and bar. When viewed on a monitor, the window signal produces a large white square in the center of the picture.

A transition between two video signals that takes the shape of a geometric pattern. X-Y panel--A routing switcher control panel that uses the X-Y model for making crosspoint selections.

Y (luminance) 
The luminance (brightness) portion of a video signal, especially component video. The formula for deriving & from the red, green, and blue signals is 0.30 R + 0.59 G + 0.11 B. 
Admittance, which is the reciprocal of impedance, the ease with which alternating current flows through a circuit.

Yellow signal 
In telecommunications, a signal sent back in the direction of a failure, indicating that the input of a network element has failed. The yellow signal varies with the DS framing used.

Y, R-Y, B-Y 
Color difference signal designation. Y corresponds to the luminance signal, R-Y corresponds to the red minus luminance signal, and B-Y corresponds to the blue minus luminance signal. These signals are derived as follows: 
Y = 0.3 Red + 0.59 Green + 0.1 Blue 
R-Y = 0.7 Red + 0.59 Green - 0.1 Blue 
B-Y = 0.89 Blue - 0.59 Green - 0.3 Red 

Y to C delay 
Relative delay or timing of the luminance channel compared to the chrominance channel in a video system. 

Y, U, V 
PAL luminance & color difference components. U and V are the names of the B-Y and R-Y color differences signals (respectively) when they are modulated onto subcarrier.