363-206-285
Circuit Pack Descriptions
Issue 3 June 2001
7-131
Timing Circuitry 7
Each TG circuit pack sends timing signals to each 24G-U OLIU. Each 24G-U
OLIU monitors the timing inputs from both TG circuit packs. The 24G-U OLIU
normally selects the timing signals from the TG selected by the SYSCTL. Each
24G-U OLIU provides timing signals derived from the incoming optical signal to
both TG circuit packs for line timing and DS1 output (BITS).
Protection Circuitry 7
The 24G-U OLIU is protection switched by the SYSCTL in response to an external
command or internal equipment fault. The 24G-U OLIU also supports protection
switching for unidirectional path switched rings at the VT and STS level.
The 24G-U OLIU interfaces with STS-1 signals from the circuit packs in the main
and function unit slots. It selects the signals from the service or protection slot of
each pair as directed by the SYSCTL.
The 24G-U OLIU provides selectors for timing signals from the TG circuit packs,
monitors these inputs, and autonomously selects either TG circuit pack. The
SYSCTL can inhibit autonomous selection and make its own selection.
Fault Detection Circuitry 7
The 24G-U OLIU circuit pack has in-service and out-of-service built-in test
capability. In-service testing is continuous and errors are reported when they
occur to the SYSCTL via the intra-shelf control bus. An out-of-service test is
performed whenever the OLIU circuit pack is inserted or recovers from a transient
failure.
The 24G-U OLIU has provisionable VT signal degrade and STS signal degrade
BER threshold capabilities for path protection switching.
Performance Monitoring 7
The 24G-U OLIU provides PM circuitry for the following performance parameters:
■ Section SEFS count for the OC-12 input
■ Line coding violation counts for the OC-12 input
■ STS-1 path coding violation counts for up to three STS-1s that are VT1.5
cross-connected.
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