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SoundExpression
Appendix M: Glossary of
Modem Communication
Terms
A
algorithm . A formula or procedure which
employs various methods defining how data
is to be used to give a prescribed result.
analog signals . Signals which can vary over a
continuous range (e.g., the human voice over
conventional telephone lines). Analog
circuitry is more subject to distortion and
noise, but it is more capable of handling
complex signals than are digital signals which
can have only discrete values.
ARQ . Automatic ReQuest for retransmission.
A type of communications link where the
receiver asks the transmitter to re-send a
block of data when errors are detected.
ANSI . American National Standards
Institute. A non-profit, private industry
association which governs most USA-
standards setting agencies.
ASCII . Acronym for American Standard
Code for Information Interchange. ASCII is
an ANSI character set. The standard ASCII
character set consists of 128 decimal numbers
(0-127) for letters of the alphabet, numerals,
punctuation marks, and common special
characters. The extended ASCII character set
extends to 255 characters and contains special
mathematical, graphics, and foreign
characters.
asynchronous communications . A method of
transmission in which one character is sent
one bit at a time; also referred to as serial
transmission.
B
Bell standard s. Refers to the U. S. modulation
protocol standards developed by the former
AT&T Bell Systems such as Bell 103 (300bps
transmission) and Bell 212A (1200bps
transmission).
bit-mapped registers . An S-register which
contains multiple bit-oriented values.
blind dialing . An automated process
whereby the modem goes off-hook and dials
without waiting for a dial tone. This is
prohibited in many countries.
block transfer control . Determines whether
or not the modem uses block or stream mode
during an MNP connection. In stream mode,
MNP sends data frames in varying length.
Block mode sends fixed data frames of 256
characters.
bps . bits per second.
break handling . Determines how the modem
responds when a BREAK signal is received
from either the DTE (Data Terminal
Equipment or computer/terminal) or the
remote modem. This is controlled by the
MNP-based AT extended command \K. A
break signal is represented on the
communications line by a steady space signal
for a significant length of time. Break signals
may be activated from the keyboard by
pressing the BREAK key or the control
(CTRL) and C keys.
C
CCITT . Consultative Committee for
International Telephone and Telegraph. This
advisory organization is part of the ITU
(International Telecommunication Union)
which is an agency of the United Nations.
Organization recently renamed International
Telecommunications Union-
Telecommunications Standard Sector (ITU-T)