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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.