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Appendix D. Glossary
61200659L1-1 MX2800 STS-1 User Manual D-9
NRZ
Non return to zero. A mode in which the digital level is low for a 0 bit and high
for a 1 bit, and does not return to zero between successive 1 bits.
out-of-band
Signaling that is separated from the channel carrying information (voice, data,
video, etc.). Typically the separation is accomplished by a filter. The signaling
includes dialing and other supervisory signals.
point-to-point
Type of communications link that connects a single device to another single
device, such as a remote terminal to a host computer.
POP
Point of presence. Physical place within a LATA (local access and transport area)
where a long distance carrier or a cellular provider interfaces with the network of
the local exchange carrier (LEC). A POP is usually a building serving as the
point of termination which houses switches and transmission equipment.
protocol
A set of rules controlling the orderly exchange of information between stations
in data communications networks or systems.
PSTN
Public switched telephone network. Usually refers to the world-wide voice tele-
phone network available for public use.
red alarm
Unframed all ones signal (keep alive signal). A red alarm is declared on detec-
tion of LOS or OOF not caused by an alarm indication signal (AIS) that persists
for more than two seconds.
remote configuration
A feature designed into ADTRAN products that allows remote units to be con-
figured from a local unit or a VT 100 compatible terminal.