Issue 3 June 2000 GL-1
Glossary
0x1
See Ring (0x1) Low-Speed Interface.
1+1
The 1+1 protection switching architecture protects against failures of the optical transmit/receive
equipment and their connecting fiber facility. One bidirectional interface (two fibers plus associated
OLIUs on each end) is designated "service,” and the other is designated "protection.” In each direc-
tion, identical signals are transmitted on the service and protection lines ("dual-fed"). The receiving
equipment monitors the incoming service and protection lines independently, and selects traffic
from one line (the "active" line) based on performance criteria and technician/OS control. In 1+1
both service and protection lines could be active at the same time. Also referred to as linear (1+1)
low speed interface.
1xN, 1x1
1xN protection switching pertains to circuit pack protection that provides a redundant signal path
through the DDM-2000 (it does not cover protection switching of an optical facility; see "1+1"). In
1xN switching, a group of N service circuit packs share a single spare protection circuit pack. 1x1 is
a special case of 1xN, with N=1. In 1x1 only one is active at a time.
2B1Q
2 - Binary, 1 - Quaternary. This means that the input voltage level can be one of 4 distinct levels
(
Note:
0 Volts is not a valid voltage under this scheme). These levels are called Quaternaries. Each
quaternary represents 2 data bits, since there are 4 possible ways to represent 2 bits.
A
ABN
Abnormal (status condition)
ACO
Alarm Cutoff — A pushbutton switch available on the user panel that can be used to retire an audi-
ble office alarm.
ACO/TST
Alarm Cutoff and Test — The name of a pushbutton on the user panel.
Active
Active identifies a 1+1 protected OC-N line which is currently selected by the receiver at either end
as the payload carrying signal or a 1x1 or 1xn protected circuit pack that is currently carrying ser-
vice. (See Standby.)
ADM
Add/Drop Multiplexer
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