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Appendix D. Glossary
61200275L1-1 TSU IQ+ User Manual D-9
ISDN
integrated services digital network. A network architecture that enables end-to-
end digital connections. The network supports diverse services through inte-
grated access arrangements and defines a limited set of standard, multipurpose
interfaces for equipment vendors, network providers, and customers. Inter-
working with a public switched telephone network is retained.
LAN
local area network. A privately owned network that offers high-speed commu-
nications channels to connect information processing equipment in a limited
geographic area.
LBO
line buildout. The introduction of gain or loss in a signal to optimize the signal
level for a receiver.
local loop
In telephony, the wire pair that connects a subscriber to a phone company end
office. Four-wire local loops are common and are used on T1 facilities.
local loopback
A type of test used to verify the operation of the local terminal equipment, the
CSU, and the connection between the two units. The signal from the DTE is
looped back by the CSU and is sent back to the DTE.
loopback
The technique for testing the processing circuitry of a communications device.
May be initiated locally or remotely via a telecommunications circuit. Device
being tested will echo back received test data. The results are compared with the
original data.
LOS
loss of signal. Defined as a line state in which no pulses are received for 175 bit
positions.
MIB
management information base. A database of network management informa-
tion used by SNMP.
modem
The equipment that connects DTE to analog (voice) communications.