P

Pacing Device or Reading Pacer - A device for the controlled exposure or indication of reading materials to promote improved reading skills. A band of light, moving pointer or occluding cover may be used. See TACHISTOSCOPE and CONTROLLED READING DEVICE

PAF - Phase Alteration by Field; an early proposed HDTV transmission system

PAL - Phase Alternate by Line. 625-line 50-field composite color transmission system, used in England, Western Europe, Scandinavia, South Africa and Australia

Palette - The display of colors available for imaging

PAL-M - Phase Alternation by Line, Brazilian broadcast standard which consists of 525 lines and 60 fields per second

Parallel - A method of transmitting several bits of data simultaneously through a communications channel

Pause (Electronic) - A cue signal different from the 50Hz or 1000Hz frame advance signal which commands the audio­visual equipment to stop automatically, thus permitting response time.

Pause Control - A mechanical device to stop tape movement temporarily during playback or recording without turning off the motor

PBX (Private Branch Exchange) - A private switching system for interconnecting a customer’s internal telephone lines extensions) with one another and with the public telecommunications networks.

Peak Detection - An acquistion mode for digital oscilloscopes that lets you see the extremes of a signal

Peak-to-peak-V[p-p] - The voltage measured from the maximum point of a signal to its minimum point, usually twice the V[p] level

Peak White - The whitest portion of a picture signal

PEI. - Picture Element, normally referred to as pixel

Period - The amount of time it takes a wave to complete one cycle. The period equals 1/frequency

Persistence - The rate of decay of the visible glow from a CRT’s phosphor, when the scanning electron beam is no longer applied. Monitors with a long persistence phosphor will have less visible flicker, but may show smearing when mages are moved on the screen

Perspective - Technique for representing 3-D objects on a 2-D surface

PGA - Professional Graphics Adaptor

Phantom Power - A method of providing power to the electronics of a condenser microphone through the microphone cable

Phase-lock-loop (PLL) - A circuit which maintains a desired frequency by means of a self-correcting loop technique

PHB - Photo-Chemical hole Burning (memory): a phenomenon where molecules absorbing Light of a specific wavelength become isomerized and create an information hold. A next-generation optical recording system, PHB could increase recording density by up to 100C times

Phone Plug - Jack or plug type most often used for microphones

Phono Plug - Jack or plug type most often used with audio amplifiers, also known as RCA Plug

Phosphor - The material which coats the inside face of a CRT. When struck by an electron beam, it glows, providing the image. The higher the quality/composition of the phosphor, the brighter and more vivid the image

Photo Coupler - An electronic component that receives and sends information by light. Free from electrical noise, photo couplers are used in telephones, inverter air conditioners and industrial machines

Photo Diode - A diode that converts optical signals to electrical signals. Used to sense brightness and distance in camcorders and for optical signal reading of remote control units and bar code readers

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Photo lnterruptor - Incorporating light-emitting and receiving devices in one package, this electronic component detects the presence or position of objects by light. Used in monitoring VTR tape and printer ink ribbons

Picture-in-Picture (PlP) - Lets you watch two shows at one time, one as the main picture, and one in a small corner of the screen.

Pixel - Picture Element. The smallest element to create an image in computer graphics; a dot

Pixel Resolution - A measurement of resolution of a television image defined in terms of discernable pixels

Platform - A standard computer workstation to which a vendor can add custom software, e.g. IBM PC, DEC MicroVAX, Apollo workstation

Playback - A device to reproduce a previously recorded program for hearing and/or viewing

Plotter - Graphics output device which uses hand-drawing instruments such as brushes or pens of different colors to print out information, usually on paper

Plug - A device on a cord for connection or attachment to a jack; various kinds are available. See JACK

Plumbicon - See TELEVISION CAMERA TUBES

POP (Point of Presence) - Location of a connection point to an Interexchange Carrier (IXC).

POTS (Plain Old Telephone Service) - Analog phone service.

Power Pack - Rechargeable DC power supply or battery pack

Pro-Amplifier (Also Pre-Amp) - An amplifier that strengthens weak signals such as those from a microphone, magnetic playback head, photo cell, or a phonograph pick-up to a level sufficient to drive a power amplifier

Pre-Out/Main In - The preamp output jack allows hook up of a signal processor such as an equalizer and then routes the modified signal back in through the main input jacks for amplification.

PRI (Primary Rate Interface) - An ISDN subscriber line, consisting of twenty-three 64Kbps B channels in North America thirty 64Kbps channels elsewhere) and one 64Kbps D channel, used for signaling purposes. (Ascend Communications, 1994)

Program Call (Electronic Learning Laboratory) - Allows the instructor through the manipulation of a single control to make announcements to students listening to specific program channels only

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Programmer (Multi-Image Devices) - A multi-channel, multi-function device used with a tape recorder, computer or perhaps its own built-in information storage device to perform certain predetermined functions when called upon to do so by the synchronizer In addition to controlling projectors, dissolve controls, etc., it can be arranged to perform other functions (often via interfaces) such as operating a motorized screen, turning on room lights, etc. It may contain the functions of a synchronizer and/or a dissolve control. Compare with SYNCHRONIZER

Program Monitor (Electronic Learning Laboratory) -Allows the instructor by means of a control to monitor the audio program stimulus before and while sending it to the students. This is usually accomplished by listening to the program through headphones and watching a Volume Unit (VU) meter

Program Stop - A cue on an audio tape (usually 150Hz separate track) capable of causing the tape recorder to pause automatically. To restart the recorder, a restart button or switch is depressed

Projection Lens (Objective Lens) - A convex lens or system of lenses that recreates an enlarged image of the transparency, objector film on a screen

Prompt - A message from the computer to the operator that a user action is required

Proportional Spacing - Character spacing where the space between characters depends upon the actual width of the characters

Proximity Effect - The increase in bass occurring with most unidirectional microphones when they are placed close to an instrument or vocalist (within 1 ft.). Does not occur with omnidirectional microphones

Pulse - A common waveform shape that has a fast rising edge, a width, and a fast falling edge

Px64 - The ITU-T’s international video standard which provides a standard algorithm for video compression and decompression. Formally known as H.261, it was adopted in December 1990.

Q

Quantizing - The process of sampling an analog waveform to convert its voltage levels into digital data.

Quartz-Iodine - See TUNGSTEN HALOGEN

R

Rack-and-Pinion Focusing - A toothed bar rack~ which engages a gear pinion) to convert the rotation of a knob to linear movement of the lens for focusing

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Rackmount - A standard method of mounting equipment; rack sides are 19’ apart so all equipment 19’ wide or less can be mounted in the rack. Equipment designated rack mountable has screw holes at the edges for mounting

RAM - Random Access Memory; the memory which is temporary, the main working storage area for the computer. If the power is turned off, the data in memory will be lost

Random Access - The ability to retrieve in any sequence slides, filmstrip frames or information on audio or video tapes or video discs regardless or original placement order

Random Access Projector - A device to permit the selection of slides for projection in any sequence desired regardless of placement order in the slide tray

Raster. A matrix of pixels or the scanning lines on a CRT which provide images

Raster Graphics - A graphics system in which the computer image is treated as a collection of dots (pixels)

Rate Controlled Speech - See SPEECH COMPRESSION AND EXPANSION

Raw Tape - A term sometimes used to describe tape that has not been recorded. Also called virgin or blank stock

RBOC (Regional Bell Operating Companies) - The “Baby Bells” created by the divestiture of AT&T. These include: NYNEX, Bell Atlantic, Bell South, Ameritech, PacTel, Southwestern Bell, and U.S. West.

Real-time Animation - Animation procedure in which screen images are drawn rapidly enough to give the viewer the impression that the image is moving

Rear Screen - A translucent screen of glass or plastic with a specially formulated coating on which the image is transmitted through the screen for individual or group viewing. The screen is between the projector and the viewer. The slide or film must be reversed or a mirror or prism used to correct the image for viewing

Receiver - An electronic device for collecting broadcast transmissions and decoding them for output on either an audio or video player/amplifier in their original form

Recorder - A device for making a permanent or temporary record of a signal or a program. It may be audio and/or video. It usually can play back or reproduce as well as record. Magnetic tape is most often the recording medium. The tape may be on open reels or in a container called a cartridge or cassette. The tape may be from 0.15~ to 2.0 wide

Reel-to-Reel - Film or tape transport in which separate supply and take-up reels are used; they may be open or enclosed

Remote Control - A device for controlling a machine or some function of a machine at a distance through wired or wireless means

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Resolution - This term relates to sharpness of an image. Some computer and video applications, like graphics or HDTV, require high resolution

Responder - A device used with some audio-visual equipment which allows a student to respond to the program; i.e. answer multiple choice questions

Retrace - The blank portion of the video signal, while the electron beam moves without producing an image

Return Key - See ENTER KEY

Reverse Video - Dark characters on a light background rather than light characters on a dark background

Review Control - A device for rapidly reversing a tape or film for a short distance to find and repeat a desired section

RF - Radio Frequency

RF Adapter - A unit which converts a composite video signal and outputs an HF channels or 4 signal; allows use of TV set in place of a monitor. Can be internal or external

RF Coax AV Output - This is a standard cable output of a video/audio signal which is limited to a maximum of 330 lines of resolution.

RF Inputs - Standard “nipple” connection used for supplying cable or antenna signal to TV.

RGB - Red, Green, Blue; the chrominance information in a video signal; 3 identical color channels

RGB Sync - Red, green, blue and sync, same as RG8 but with additional sync channel

RGB Video - Computer video output which can be analog or digital. Analog RGB video has 3, 4, or 5 wires; one for the red, one for the green, one for the blue VIDEOs and one or two for the SYNC. Digital RGB video always has 4 or wires

RISC - Reduced Instruction Set Computer: a chip architecture designed to optimize speed and power by simplifying the internal computer instructions

RMS - Root mean square

Roll - Loss of vertical sync which causes the picture to move up or down the screen

Rollabout - A complete single monitor system package contained in a cabinet with picture-in-picture capability to show multiple video inputs.

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ROM - Read-Only Memory, permanent memory which can be read by the CPU but cannot be written to, usually reserved for internal programs which the computer uses to carry on its functions, It is only entered once, normally by a manufacturer, and may not be altered or removed, It is permanent and is retained even when power is lost.

RP-125 - An SMPTE parallel component digital video standard.

RPM - Revolutions per minute

RS-170A - A video standard which ensures proper synchronization and levels of video signals and components

RS-232 - Communications interface standard; plugs and sockets for connecting computer components to allow interaction: nonvideo serial communications standard

RS-250B - In telecommunications, a transmission specification for NTSC video and audio.

RS-330 - EIA technical standard which provides details for industrial CCTV

RS-422 - A standard, balanced interconnection scheme for serial data communications

RS-449 - Transmission interface between the codec and the transmission link that typically connects to a T1 multiplexer A user RS-449 port may also be available for data transfer

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