GL-10
Issue 5 June 2000
363-206-208
Glossary
IR
Intermediate Reach.
IS
In Service — One possible state of a DS1, DS3, or EC-1 port. Other possible states are
"auto" (automatic) and "nmon" (not monitored).
ISDN
Integrated Services Digital Network.
IS-3
A proprietary interface provided by the 21D optical line interface units. Used for OC-3/
OC-12 intershelf interworking.
ISO
International Standards Organization. A standards organization that creates, writes
compiles and distributes standards for mant systems and interfaces that must be used
in international technology and business communities. See OSI.
ITU
International Telecommunications Union. An international advisory committee under
United Nations’ sponsorship that has composed and recommended for adoption
worldwide standards for international communications. The ITU consists of the ITU-R
(radio, that is, free space) and the ITU-T (telecommunications, meaning any mode that
uses a medium other than radio. Fiber optics and coaxial cable are examples of
transmission technology falling under ITU-T.) The International Telecommunications
Union replaced the CCITT. See CCITT.
J
Jitter
Timing jitter is defined as short-term variations of the significant instants of a digital sig-
nal from their ideal positions in time.
L
LAN
Local Area Network.
LAPD
Link Access Procedure "D".
laser
A semiconductor device. Used on a circuit pack as a source of coherent light for
communications.
Summary of Contents for DDM-2000 OC-12
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