363-206-305
Circuit Pack Descriptions
Issue 3 June 2000
7-47
The red FAULT LED lights by the SYSCTL on detection of BBG19 DS3 circuit
pack failure. In the event of an incoming DS3 signal failure, this LED will flash on
and off. The green ACTIVE LED lights when the circuit pack is active (in-service).
General Description of Operation
7
NOTE:
DS3 access is through a BNC connector on the faceplate.
The DS3 Data Services Interface circuit pack (BBG19) provides a mapping
between a DS3 low-speed signal from a DS3 Data Services Device and an
internal STS-1 signal. The BBG19 provides the same functions as the BBG4B, but
provides DS3 access through two BNC connectors on the faceplate. DS3 access
to the BBG4B is through BNC connectors on the rear of the shelf.
In the transmit direction, the incoming DS3 signal can be either formatted or
unformatted (clear channel). The BBG19 DS3 circuit pack accepts one 44.736
Mb/s bipolar 3-zero substitution (B3ZS) coded DS3 signal. The incoming DS3
signal is mapped into an STS-1 payload envelope using SONET asynchronous
mapping. The STS-1 path overhead and pointer bytes are added and the resulting
signal is sent to the high-speed OLIU circuit pack.
In the receive direction, the STS-1 signal from the OLIU circuit pack goes through
STS-1 pointer interpretation, and path overhead is removed and processed.
After the DS3 signal is recovered from the STS-1 payload envelope, the DS3
performance bits (P-bits) may be monitored and corrected through a provisionable
violation, monitor, and removal (VMR) function.
NOTE:
Protection switching must be done externally to the FiberReach multiplexer.
The BBG19 DS3 circuit pack provides enhanced DS3 performance monitoring
capabilities with FiberReach software releases 3.1 and later.
The BBG19 DS3 circuit pack provides bidirectional transport of one DS3 signal
through DDM-2000 OC-3 in either CC mode, VMR mode, or VM mode, by
mapping the DS3 into an STS-1 signal. The BBG19 DS3 performs maintenance
and provisioning functions associated with the STS-1 and DS3 signals and
provides access to the STS-1 path overhead. It interfaces to the OLIU at the
STS-1 rate, to the data services device, and to the SYSCTL. When provisioned for
the CC mode, the DS3 can transport any DS3 rate signal that meets specified
electrical interface requirements. When provisioned for the VMR or VM mode, the
DS3 signal must meet both electrical and DS3 frame format requirements.
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