Circuit Pack Descriptions
7-70 Issue 8.0 July 2002
Timing and Control Functions 7
The IS3 (1.3 STD) circuit pack performs the following timing and control functions:
a. Selects the primary or secondary 155.52 MHz timing signal from the TG3
(DS1) circuit packs
b. Provides selector circuitry for high speed protection switching
c. Performs internal fault detection and interfaces with the LNCTL circuit pack
using the board controller local area network (BCLAN)
d. Provides IS-3 and STS-3/3c loopbacks
e. Stores inventory information (CLEI code, serial number, etc.)
f. Controls the circuit pack faceplate FAULT LED.
Maintenance Signal Functions 7
The IS3 (1.3 STD) circuit pack performs the following maintenance signal
functions:
a. Detects incoming (from the lightguide cross-connect panel) IS-3 loss of
signal (LOS), loss of frame (LOF), and signal degrade (SD) based on the
B2 error rate
b. Inserts STS-1 path AIS in each STS-1 tributary of the STS-3/3c signal
(155.52 Mb/s) transmitted toward the OC48 TRMTR circuit pack when
incoming (from the lightguide cross-connect panel) IS-3 LOS or LOF is
detected
c. Inserts STS-1 path AIS in each STS-1 tributary of the STS-3/3c signal
transmitted toward the OC48 TRMTR circuit pack and in the IS-3 signal
transmitted toward the lightguide cross-connect panel when an internal
fault is detected.
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