Graphics

Information in the form of pictures or images. Also, the display of pictures or images on a computer’s display screen.

Guard Band

Narrow frequency band left unused between adjacent channels to minimize interference.

H

Half Duplex

Data transmission in which data may flow in either direction at one time, but not both directions simultaneously. Transmission direction is alternatively switched to allow two way flow of data.

Handshake

A predetermined interchange of signals between two devices to establish conditions for a transfer of data.

Hardware

The electronic or electro-mechanical devices in a computer system as opposed to the programs or software.

Hardware Handshaking

The use of special RS-232 signals to halt or commence the flow of data between two computers or terminals, between computers and modems or between facsimile machines. See also Software Handshaking, RTS and CTS

Harmonics

Frequencies which are integer multiples of some fundamental frequency.

Harmonic Distortion

A line impairment caused by equipment which distorts the original signal at multiples of the same fundamental frequency.

Hexadecimal Numbers

A number system with a base of 16. The first ten digits are represented by 0- 9 while the last six digits are represented by A-F. Hexadecimal numbers can be easily translated from binary numbers and are easier for humans to understand and read than are binary numbers.

HDLC

High Level Data Link Control. Communications protocol developed by the International Standards Organization.

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