3Com 56K manual Glossary

4GLOSSARY

Class 1/EIA-578An American standard used between facsimile application programs and facsimile modems for sending and receiving Class 1 faxes.

Class 2.0/EIA-592An 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 An error-detection technique consisting of a cyclic algorithm performed check (CRC) 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 A table of values assigned for each character during a call under data table 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 In this manual, the term applies to modems that establish and control equipment (DCE) the data link via the telephone network.