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Glossary of Terms

Glossary of Terms

Packet Switching
Data transmission method that divides messages into standard-sized packets for greater efficiency of routing and transport through a network.
PAL
Acronym for Phase Alternate Line; the standard color system used throughout Western Europe except in France. PAL-M is the standard system in Brazil. It uses an interlaced format with 25 frames per second and 625 lines per screen.
PAL-M
Brazilian version of PAL. Broadcast standard with 525 lines and 60 fields per second.
Palette
In digital video and computer graphics, the total number of colors available for use in a presentation or program.
Pan
To pivot a camera in a horizontal direction, tilt is to pivot in the vertical direction.
Parallel
A method of transmitting several bits of data simultaneously through a communications channel.
Passive Addressing
Standard method of providing a passive matrix LCD panel with drive signals, enables one horizontal row of imagesels along all of the vertical columns to be written to at a time. See "Passive Matrix".
Passive Graphics
A computer graphics operation that transpires automatically and without operator intervention.
Passive Matrix
A form of LCD driving approach that relies on overlapping transparent conductive traces to deliver the drive signal to the common vicinity (the equivalent of imagesels) outlined by two traces. The traces are arranged as a network of vertical columns and horizontal rows (a matrix) on opposing plates of glass so that none of them touch across a thin gap of liquid crystal material. See "Active Matrix".
PBX
Private Branch Exchange. A telephone switch usually located on a customer's premises, connected to the telephone network but operated by the customer. A PBX provides pooled access to a given number of inside (extension) lines in a smaller number of outside lines (trunks). Often, outgoing calls are dialed directly; incoming calls are handled by an operator or switched automatically by the PBX software.
PC
Acronym for Personal Computer. (Where have you been?)
PCB
Acronym for Printed Circuit Board.
PDA
Acronym for Personal Digital Assistant, such as a Palm or Windows CE device.
Peak
The highest or lowest level of signal strength, as determined by the height of the signal's waveform.
Peak Detection
An acquisition mode for digital oscilloscopes that lets the user see the extremes of a signal.
Peak-To-Peak
Abbreviated "p-p". The Amplitude (voltage, for example) difference between the most positive and the most negative excursions (peaks) of a signal.
Peak White
The whitest portion of a picture signal.
Peaking
A means of compensating for mid and high frequency RGB video bandwidth response in data monitors and projectors and for signal losses due to cable capacitance. When using the peak enhancements, use the following guidelines for proper output settings: Use 50% with all computer frequencies between 15-125 kHz at any cable length. Use 100% with high frequency computers of 36 kHz or higher with cable lengths 75 feet or greater.
Peaking Control
Extron's peaking control compensates for mid and high frequency RGB video bandwidth response in data monitors and projectors and for signal losses due to cable capacitance. By using the peaking control a noticeably sharper picture will be seen on all displays regardless of cable lengths, but, on lengths of 250 feet or more with any signal ranging from 15-125 kHz, the peaking control should probably be set at 100%. Please note that 100% peaking may provide over enhancement on short cable runs. Also called "sharpness" control.
Pentium
Intel's "586" CPU chip competitive to RISC technology.
Performa
A mid-range PC style computer from Apple Computer, Inc.
Performance Objective
A specifically defined goal that can be measured and observed.
Peripheral
External devices controlled by the computer, e.g., keyboard, printer, mouse, etc.
Peripheral Device
A device that a CPU communicates with, such as a printer, mouse, external disk drive, interface, etc.
Persistence
In essence, the "staying power" of a lighted phosphor, since a phosphor begins to dim after being excited by the electron beam. A long-persistence screen allows the phosphor to dim more slowly.
Personal Computer (PC)
A microcomputer designed for use by an individual person (or one at a time).
PGA
Professional Graphics Adapter, Resolution 640 x 400. Professional graphics adapter. Early IBM analog graphics adapter found in the PC AT series. The PGA was capable of producing 256 colors.
Phase
The relative timing of one signal to another, usually expressed in degrees of shift.
Phone Plug
A 1/4" audio plug used as a speaker connector.
Phono Plug
A plug most often used with line level audio signals. Also known as an RCA plug.
Phosphor
The chemical coating on the inside of the CRT screen that generates light (monochrome or color) when struck by an electron beam. Each dot on the screen is actually a phosphor that glows for a period of time. The higher the quality/composition of the phosphor, the brighter and more vivid the image. See persistence.
Picture Control
Same as level control.
Picture Tube
The CRT used to produce and display video images. The visible image is created by variations in intensity of an electron beam which scans the phosphor-coated interior surface of the tube.
Pin
The connectors used in computer/projector cables. Cables are often identified by the number of pins they contain. A typical computer video cable has 15 pins, and is called a 15-pin video cable.
Pin Cushion
The inward or outward (curved) appearance of the edges of a display.
Pin Outs
A list of control functions assigned to the pin numbers on a remote control connector.
Pink Noise
A uniform noise level over a given bandwidth, usually in the video frequency range.
Pinout
An illustration or table that names signals, voltages, etc. that are on each pin of a connector or cable.
Pit
The microscopic physical indentation that "holds" data in the information layer of a video-disc.
Plain Old Telephone Service
Conventional analog telephone lines using twisted-pair copper wire. This is used to provide residential service.
Plasma (monitors or projectors)
Plasma Imaging: Plasma technology uses phosphor stripes painted in Barrier Ribs (one stripe per color--red, green and blue) and these ribs or stripes are charges with a neo gas light mixture to create an image on a flat surface (no screen required). More information on Plasma technology may be found at www.plasmavision.com.
Plenum Cable
Cable having a covering that meets the UL specifications for resistance to fire.
PLL
Acronym for Phase Locked Loop
PLUGE
Picture Line Up Generation Equipment - This is the name of a test pattern that assists in properly setting picture black level. PLUGE can be part of many test patterns. The phrase and origination of the test signal are both credited to the BBC.
Polarity
The positive and negative orientation of a signal. Usually refers to the direction or to a level with respect to a reference. (e.g. positive sync polarity means that sync occurs when the signal is going in the positive direction.)
Polarizer
An optical component that filters out light according to its wave direction.
Polarizing Screen
A projection screen that takes advantage of the differences between the polarized projected light and randomly polarized background light. By reflecting virtually all of the vertically polarized light from the projector while absorbing the random background light, especially the horizontally polarized floor and table surface reflections, the effective contrast ratio of a system can be greatly enhanced. With such a screen, true "room light visible" projection displays are quite feasible.
Polysilicon
Small multicrystalline form of silicon used in silicon-gate MOS technology that is electrically conductive and optically transparent.
Port
A connector on a computer or peripheral that allows it to be connected to something else. Typical ports to be found on a computer include serial, parallel, disk drive, video and external keyboard.
Post Production
The state of production of a film or video program in which editing or assembling from raw footage occur.
POTS
Acronym for Plain Old Telephone Service.
Power Down
A modern term for turning something off. Applies most commonly to electronics.
Power (Electrical)
The dissipation of heat by passing a current through a resistance. Measured in Watts (W), it is expressed by Ohm's law from the two variables: Voltage (E) and Current (I). i.e. P = 1xR, or, P = E x I.
Power PC
A microprocessor for the new generation of PC's and workstations from IBM, apple and DEC. Is also the same processor in the PowerMac PCs.
PowerBook
Apple's Macintosh version of a laptop PC.
Pre-Amp
Pre-amplifier. An electronic circuit that raises a weak signal high enough to be fed into an amplifier.
Pre-Amplifier
See pre-amp.
Preproduction
The first stage of production in which budgeting, flow-charting, story-boarding, script writing, etc., occur. Included are all design tasks which happen prior to actual production of a film or video program/presentation.
Presentation
A speech given to one or more people utilizing some sort of visual support. (Hopefully, for all involved, an InFocus projector.)
Presentation Device
A general term used to define a video projector or data monitor.
Primary Colors
Colors, usually three, which are combined to produce the full range of other colors within the limits of a system. All non-primary colors are mixtures of two or more of the primary colors. In television, the primary colors are specific sets of red, green and blue.
Proc Amp
Processing amplifier. An electronic device which stabilizes or rebuilds signals.
Processing
The manipulation of data from one state to another.
Processing Amplifier
See proc amp.
Production
The stage when video, film, or software is actually shot or created.
Program
A set of instructions designed to make a device, or a system, perform a specific function or functions.
Programmable Read Only Memory
A type of novolatile, semiconductor read-only memory component that can be programmed by the user one time and only read from that time on. A memory whose contents is not lost when power is removed, but can be reprogrammed using a special PROM programmer, or "burner". Also see EPROM and EEPROM.
Progressive Scan
Another method of displaying images on the TV screen. The beam of electrons emitted by a CRT scans the entire screen every 1/30th of a second. (See non-interlaced).
PROJECTION
The process of presenting visual media by light transmitted through an optics system to a viewing screen.
PROM
Acronym for Programmable Read Only Memory.
Pseudo Color
Also known as "false color" or "colorized". The colors projected do not correspond to the original image. Products use a single, colorized LCD, often with purple for dark shades and yellow for light shades - purple background, yellow foreground. Thus, what should be blue may turn out looking yellow, green may look purple, etc.
Public Domain
Being free of patent or copyright. Public domain software is available, free of charge, to anyone who wants to use it.
Pulse
A common waveform shape that has a fast rising edge, a width, and a fast falling edge.
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