US Robotics COURIER - Page 196

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COURIER HIGH SPEED MODEMS
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 proces-
sor. 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.
Throughput
The amount of actual user data transmitted per second without
the overhead of protocol information such as Start and Stop bits
or frame headers and trailers. Compare characters per second.
Transmission Rate
Same as Bit Rate.
V.21-Fax
A CCITT standard for facsimile operations at 300 bps.
V.21-Modem
A CCITT standard for modem communications at 300 bps.
Modems made in the U.S. or Canada follow the Bell 103 stan-
dard. However, the modem can be set to answer V.21 calls from
overseas.
Glossary G-11