Phase Alternating Line. Broadcast standard developed in Germany in 1963 and adopted in 1967. It’s used in many countries throughout Europe including the UK and transmits 576 viewable lines at 25 frames per second interlaced.

A method to fit source material of a different resolution or aspect ratio onto another. Sometimes used with computer input when the input resolution exceeds the resolution of the display device. Used extensively for broadcast and DVDs, it simply crops the sides of widescreen material and the transfer operator chooses the best part of the frame to show. Often an electronic camera pan is used to change the area being shown. This is used when characters are talking to each other but one is off screen due to cropping and they become the focus of the shot.

Pulse Code Modulation. A technique for representing analog frequencies digitally, developed in 1937 by Alec Reeves for ITT France. The most common variant is ADPCM, Adaptive Differential Pulse Code Modulation, which compresses a signal dynamically. It does so by only storing the difference between the current and previous sample and varying the granularity of those differences.

A data reduction method that uses the lack of sensitivity of human senses to certain characteristics. Visually, color undersampling (4:1:1) is an example where a person’s eyes are more sensitive to grayscale information than color, therefore less color information is needed for a given representation. Aurally, masking is a psychoacoustic phenomenon where a sound of less intensity but close in frequency cannot be discerned by a listener and that sound can be dropped from the data representation.

The disposition of humans to amalgamate sequential still images into perceived motion. For most people, this occurs at around 16 fps.

The characteristic of when a wave is at its peak, trough, or zero point going up or down. Measured in degrees. Two sine waves of the same frequency that are 180 degrees out of phase will cancel each other out, yielding no signal.

A direct-view, flat-panel display that uses ionized gas to emit ultraviolet light that then excites phosphors. Plasma is a state of matter like solid, gas or liquid. Plasma screens are challenged by latency issues without a priming voltage, which causes manufacturers to leave a voltage running across a cell in order for it to change state quickly enough to update a picture. This tends to boost black levels as every pixel is partially on all the time. This is why plasma contrast ratios aren’t as high as CRT although still very good. Also, because plasma uses phosphors it is susceptible to possible burn-in. Plasma is subject to performance issues at higher altitudes of operation such as fan buzzing and increased power consumption.Â

Picture Line-up Generation Equipment. A test pattern used to set a display’s black level. Comes in many variations but is usually comprised of three black bars where the darkest should not be visible.

One of several projector display technologies. Monochrome Poly-Si LCDs are typically placed in each of the three color (red, green, blue) light paths inside a projector to produce a color image from a common light source. Poly-Si technology is a bit faster than the Active Matrix TFT providing slightly smoother video.

With audio amplifiers, the amount of power sent to drive the speakers. Peak output is quite often specified, which is somewhat misleading compared to the average amount of power an amplifier can continously produce (RMS rating).

A zoom lens that is driven by a motor and controlled from the projector's control panel and/or remote control.

A switching device used to select a line-level audio signal for amplification. Sometimes offers signal processing as well.

A display mode in which all the horizontal lines of an image are displayed at one time in a single frame, unlike an interlaced scan in which a frame consists of two separate fields with the first field consisting of odd horizontal lines and the second field even horizontal lines. Progressive scan is used by projectors, computer monitors, HDTV systems, and some digital camcorders. Progressive Scan requires a faster horizontal scan frequency than interlaced images of the same resolution

A projector is a device that integrates a light source, an optics system, electronics and display(s) for the purpose of projecting an image from a computer or video device onto a wall or screen for large image viewing. These devices attach to a computer or video device as you would connect a monitor or television.

Program and System Information Protocol. ATSC standard A/65B for sending system and program guide information via DTV broadcasts or cable.

Study of how humans hear. Used to find ways to discard sound information that is not heard and reduce data requirements for sound reproduction.Â

Personal Video Recorder. See DVR.