4
G
LOSSARY
Class 1/EIA-578
An American standard used between facsimile application programs
and facsimile modems for sending and receiving Class 1 faxes.
Class 2.0/EIA-592
An American standard used between facsimile application programs
and facsimile modems for sending and receiving Class 2.0 faxes.
CO
See central office.
COM port
See serial port, EIA-232.
cps
See characters per second.
CPU
Central processing unit.
CRC
See cyclic redundancy check.
cyclic redundancy
check (CRC)
An error-detection technique consisting of a cyclic algorithm performed
on each block or frame of data by both sending and receiving
modems. The sending modem inserts the results of its computation in
each data block in the form of a CRC code. The receiving modem
compares its results with the received CRC code and responds with
either a positive or negative acknowledgment. In the ARQ protocol
implemented in 3Com high speed modems, the receiving modem
accepts no more data until a defective block is received correctly.
data communications
A type of communications in which computers and terminals are able
to exchange data over an electronic medium.
data compression
When the transmitting modem detects redundant units of data, it
recodes them into shorter units of fewer bits. The receiving modem
then decompresses the redundant data units before passing them to
the receiving computer.
data compression
table
A table of values assigned for each character during a call under data
compression. Default values in the table are continually altered and
built during each call: the longer the table, the more efficient
throughput gained.
If a destructive Break is sent during a call (see the &Y command),
causing the modems to reset the compression tables, you can expect
diminished throughput.
data communication
equipment (DCE)
In this manual, the term applies to modems that establish and control
the data link via the telephone network.
