Support

Glossary of Terms

Glossary of Terms

Radio Frequency
RF. The range of frequencies used for electromagnetic transmission (e.g. radio and TV).
RAM
Acronym for Random Access Memory.
Random Access
The ability to retrieve any piece of data on a storage medium in very little time.
Random Access Memory (RAM)
RAM is volatile memory that can be written to and read from. The working memory where active programs and data are stored. If the power is turned off, the data in memory will be lost. See PROM. The largest part of a computer's memory used in most daily tasks; can both read and write information and be amended or updated by the user.
Raster
A Rectangular array of imagesels. Lines and rows of dots such as on the illuminated face of a video screen. The scanned or illuminated area on a CRT on which a picture is produced. A matrix of imagesels or the scanning lines on a CRT.
RCA
Also called Composite, RCA jacks are a common connection interface for audio and video sources.
RCA Plug
A plug most often used with line level audio signals and composite video.
Read
To input data into a computer from a peripheral device, such as a disk or tape. A read is actually both an input and an output, since information is being output from the device and input into the computer.
Read-Only Memory (ROM)
A computer storage medium that allows the user to read or retrieve and use information but not write or record to it. A small part of the computer's memory in which the necessary operating information is recorded in such a way as to allow it to be retrieved and used (read), but that does not allow it to be recorded (written) to.
Real Time
The transfer of data that returns results so quickly in actual time that the process appears to be instantaneous.
Rear Projection
Projecting an image through a translucent screen material for viewing from the opposite side. As opposed to front projection.
Rear Screen
A translucent screen with a specially coating which allows an image to be projected through the screen, rather than onto the surface of the screen.
Rear Screen Projection
A presentation method in which the image is projected through a translucent screen toward the audience. The slide or film must be reversed, or a mirror must be used to correct the image for rear screen presentation. In some video or computer projectors, the image can be reversed electronically.
Receiver (Rx)
An electronic device which enables a particular videoconference signal to be separated from all others being received by an earth station, and converts the signal format into a format for video, voice or data.
Reflections
With video signals, reflections can be caused by energy that is not absorbed by the load (or a termination) and is reflected back and possibly combined with the original signal. Reflection signals can occur when the impedance does not match (because of wrong termination or mixing of cable impedance). Some of the undesirable results of reflection include: Y/C delays, color smearing, ringing on luminance (but not on color), ghosts, etc.
Refresh Rate
Many dynamic memory devices require a periodic "pumping up" of the stored information and this term refers to the required frequency of such memory maintenance.
Relay
A device that acts like a switch and is controlled by a current. The relay switch contacts then control another circuit, or pass a signal, etc. Most types of relays are solid state or electromagnetic.
Remote
A small handheld device separate from the projector itself containing projector controls such as volume, brightness, etc.
Remote Control
A device for controlling the function of a machine at a distance. May be wired or wireless.
Replicates
Copies of a videodisc that are produced or pressed from the stamper disc.
Replication
The process of mass reproduction of prerecorded CDs or videodiscs.
Repurchasing
The process of amending the content of an existing program to accomplish a task other than the one for which it was originally created.
Repurposing
The process of amending the content of an existing program to accomplish a task other than the one for which it was originally created.
Resolution
The measurement of a computer screen or projected image measured by the number of imagesels wide by the number of imagesels high. More imagesels per unit of area produce a higher resolution giving more detail in the display of an image.
Resolution (Horizontal)
The amount of detail in a horizontal direction in a video image. It is expressed as the number of distinct vertical lines, alternately black and white, that can be seen in 3/4 the width of the picture. This information is usually derived from observation of the vertical wedge of the test pattern. Horizontal resolution depends on the high-frequency amplitude and phase response of the pick-up equipment, as well as the transmission medium and the monitor itself.
Resolution (Vertical)
The amount of resolvable detail in a vertical direction in a video image. It is expressed as the number of distinct horizontal lines, alternately black and white, that can be seen in a test pattern. Vertical resolution is primarily fixed by the number of horizontal scanning lines in a frame.
Retrace
During the scanning of a picture onto a screen, scan lines are produced from left to right. Before scanning the next line, the electron beam must get back to the left side of the screen. This is called "Retrace". The beam must be turned off (blanked) during retrace time. See "horizontal blanking" and "vertical blanking".
Retrace Time
The minimum time required to move the scanning beam from the right side to the left side of the CRT screen.
RF
Acronym for radio frequency.
RF Adapter
A device that allows video and audio signals from a VTR or computer to be shown on a standard TV receiver. This device produces comparatively poor resolution and picture quality. Also called RF converter.
RF Control
A medium of remote control from which signals are sent to the controlled equipment via data pulses modulated on an RF carrier signal.
RGB
Red, Green, Blue; the chrominance information in a video signal; the primary colors from which all other colors can be construed.
RGB Monitor
A color monitor that uses color "guns" for red, green and blue to produce a high-quality picture.
RGB Sync
RGBS. Red, blue and green, the chrominance information in a video signal, with the addition of a sync channel.
RGB Video
A form of color video signal (red, green, blue) distinctly different from the composite color video used in standard television sets. RGB can be displayed only on a color monitor that has a separate electron gun for each of these primary colors. Some color television sets use only one gun. RGB monitors are noted for their crisp, bright colors and high resolution. RGB Video can be four different ways. RGsB (sync is on the green signal), RGBS (sync is separate from the colors), RGBHV (sync is separate from the colors and the horizontal and vertical are separate signals) and RsGsBs (sync on red, green and blue).
RISC Technology
A Reduced Instruction Set Computer (RISC) is based on a microprocessor technology that simplifies information processing through a reduced set of instruction formats. It is known for its fast execution of CPU instructions.
Rise Time
The time required for a signal to go from 10% to 90% of its maximum amplitude level.
RMS
Acronym for Root mean square.
ROM
Read Only Memory. Permanent memory that can only be loaded once, normally by a manufacturer. Contents may not be altered or removed. See PROM, EPROM and EEPROM. Usually reserved for internal programs which the computer uses to carry on it's functions. It can only be entered once, normally by a manufacturer, and may not be altered or removed. It is permanent and retained even when power is lost.
Root mean square
The square root of the average of the squares of the values of a periodic quantity taken through out one complete period. It is the effective value of a periodic quantity.
RS-170A
EIA technical standard NTSC color TV. A video standard that ensures proper synchronization of video signals and components.
RS-232
An Electronic Industries Association (EIA) serial digital interface standard specifying the characteristics of the communication path between two devices using D-type connectors. This standard is used for relatively short range communications and does not specify balanced control lines. A serial control standard with a set the number of conductors, data rate, word length, and type of connector to be used. Also specifies component connection standards with regard to computer interface. Also called RS-232-C, which is the third version of the RS-232 standard, which is functionally identical to the CCITT V.24 standard.
RS-232C
A standard serial interface (cable) that connects a computer and its peripherals.
RS-330
EIA technical standard which provides details for industrial closed circuit television (CCTV).
RS-422
An EIA serial digital interface standard which specifies the electrical characteristics of balanced (differential) voltage digital interface circuits. This standard is usable over longer distances than RS-232. This signal governs the asynchronous transmission of computer data at speeds of up to 920,000 bits per second.
Back to Top