ADTRAN DSU III ARdc User Manual page 122

Glossary
scrambler
A device that transposes or inverts signals, or otherwise encodes a message at the trans-
mitter, to make it unintelligible at a receiver not equipped with an appropriately set
descrambling device.
synchronous data link control
SDLC. A bit-oriented synchronous communications protocol developed by IBM where
the message may contain any collection or sequence of bits without being mistaken for a
control character.
service
The provision of telecommunications to customers by a common carrier, administration,
or private operating agency using voice, data, and/or video technologies.
simple network management protocol
SNMP. A control and reporting scheme widely used to manage devices from different
vendors. SNMP operates on top of the Internet protocol.
start bit
In asynchronous data communications, characters are sent at arbitrary intervals. In order
for the computer to make sense of what is coming in, each character starts its transmission
with a start bit. This way if the first bit of the character to be transmitted is a 0, the fact of
receiving a start bit (always a 1) tips off the computer that the next bit is part of a transmit-
ted character and not just part of the inter-character gap. See stop bit.
stop bit
The stop bit is an interval at the end of each asynchronous character that allows the receiv-
ing computer to pause before the start of the next character. The stop bit is always a 0. See
start bit.
switched
In regard to DSU/CSUs, the ability to perform the functions of establishing and releasing
connections on a per call basis between two or more circuits, services, or communications
systems. The DSU III S2W and DSU III S4W are examples of Switched 56 DSU/CSUs.
synchronous
Communications in which the timing is achieved by sharing a single clock. Each end of
the transmission synchronizes itself with the use of clocks and information sent along with
the transmitted data.
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