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Glossary
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Log on
To connect to or access a bulletin board or videotex system.
Log Off
To disconnect from a bulletin board or videotex system.
Longitudinal Redundancy Check
Error detection technique that consists of a byte where each bit is calculated on the basis of the
parity of all bits in the block in the same position.
Loopback
Directing signals back toward the source at some point in the communications path.
M
Mailbox
A term used to describe the holding, by a bulletin board, videotex or electronic mail system, of
electronic messages (mail) for a user. Usually, the system will announce if the user has any
unread mail when she/he logs on.
Mainframe
Large scale computer system composed of a large number of peripherals and comprehensive
software.
Mark
One of the two possible states of a binary data element. The closed circuit and idle condition in a
teleprinter circuit. Also see Space.
Modem
Modulator/Demodulator. A device to convert data from a computer or terminal into a form
suitable for transmission across a telephone system.
Modem Eliminator
A usually passive device which takes the place of a modem between a local terminal which
requires a modem and a computer.
Modulate
To modify or alter a signal so as to transmit information. For example, conventional broadcast
radio transmits sound by modulating the amplitude (Amplitude Modulation, or AM) or the
frequency (Frequency Modulation, or FM) or a carrier signal. See also Demodulate and Modem.
Monitor
A program or device used to observe an operation without interfering with the operation.