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COURIER HIGH SPEED MODEMS
J-12 Glossary
Start/Stop Bits
The signaling bits attached to a character before the character is
transmitted during Asynchronous Transmission.
SDLC
Synchronous Data Link Control. A protocol developed by IBM
for software applications and communicating devices operating
in IBM's Systems Network Architecture (SNA). The protocol
defines operations at the link level of communications, for
example, the format of data frames exchanged between
modems over a phone line. See Bisync, Protocol, HDLC.
Synchronous Transmission
A form of transmission in which blocks of data are sent at
strictly timed intervals. Because the timing is uniform, no Start
or Stop bits are required. Compare Asynchronous
Transmission.
Some mainframes only support synchronous communications
unless their owners have installed a synchronous adapter and
appropriate software.
Terminal
A device whose keyboard and display are used for sending and
receiving data over a communications link. Differs from a
microcomputer in that it has no internal processing capabilities.
Used to enter data into or retrieve processed data from a system
or network.
Terminal Mode
An operational mode required for microcomputers to transmit
data. In Terminal mode the computer acts as if it were a stan-
dard terminal such as a teletypewriter, rather than a data
processor. Keyboard entries go directly to the modem, whether
the entry is a modem command or data to be transmitted over
the phone lines. Received data is output directly to the screen.
The more popular communications software products control
Terminal mode as well as enable more complex operations,
including file transmission and saving received files.