363-206-285
Circuit Pack Descriptions
Issue 3 June 2001
7-123
Timing Circuitry 7
Each TG circuit pack sends timing signals to each 22G-U/22G2-U/22G3-U/22G4-
U
OLIU. Each 22G-U/22G2-U/22G3-U/22G4-U OLIU monitors the timing inputs
from both TG circuit packs. The 22G-U/22G2-U/22G3-U
/22G4-U OLIU normally
selects the timing signals from the TG selected by the SYSCTL. Each 22G-U/
22G2-U/22G3-U
/22G4-U OLIU provides timing signals derived from the incoming
optical signal to both TG circuit packs for line (formerly loop) timing and DS1
output (BITS).
Protection Circuitry 7
Optional 1+1 nonrevertive unidirectional line protection switching compliant with
SONET specifications is provided. The 22G-U/22G2-U/22G3-U
/22G4-U OLIU is
protection switched by the SYSCTL in response to an external command,
incoming optical signal failure, or internal equipment fault. The 22G-U/22G2-U/
22G3-U
/22G4-U OLIU circuit pack is protection switched with the OC-3 line.
The 22G-U/22G2-U/22G3-U
/22G4-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 22G-U/22G2-U/22G3-U
/22G4-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 22G-U/22G2-U/22G3-U/22G4-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 22G-U/22G2-U/22G3-U
/22G4-U OLIU has provisionable VT signal degrade
and STS signal degrade BER threshold capabilities for path protection switching.
Performance Monitoring 7
The 22G-U/22G2-U/22G3-U/22G4-U OLIU provides PM circuitry for the following
performance parameters:
â– Section SEFS count
â– Line coding violation counts
â– STS-1 path coding violation counts.
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