363-206-305
Circuit Pack Descriptions
7-48
Issue 3 June 2000
Detailed Description of Operation
7
Transmission Circuitry
7
Transmit Direction.
7
Figure 7-20 provides an overall block diagram of the BBG19
DS3 circuit pack. The transmit direction is the direction toward the STS-1 signal,
and receive direction refers to the direction toward the data services device. In the
transmit direction, the BBG19 DS3 receives an incoming B3ZS encoded DS3
signal from the data services device. BNC connectors on the faceplate of the
BBG19 provide input and output for the data services signal. The BBG19 DS3
receiver performs equalization recovery. The MUX circuitry performs B3ZS
decoding, optional automatic DS3 AIS insertion, and a provisionable VMR
function, then synchronizes and maps the DS3 to the STS-1 rate. The DS3 signal
is then synchronized to the STS-1 payload rate, STS-1 path overhead is inserted,
and an STS-1 rate signal is transmitted to an OLIU pair.
Receive Direction.
7
The BBG19 DS3 receives STS-1 data from the OLIUs, selects
one STS-1, performs pointer interpretation, processes and removes the path
overhead, desynchronizes the embedded DS3, provides a provisionable VMR
function, and then B3ZS encodes the signal for transmission to the data services
device. A jumper allows the user to insert or remove an LBO network (225 ft. of
734A-type cable equivalent) to provide the required signal level and shape at the
data services device.
VMR Function
7
Before the DS3 signal is B3ZS-encoded (receive) or decoded (transmit), a VMR
function can be provisioned via the control circuitry for one of three possible
modes. These three modes are as follows:
â–
VMR with DS3 AIS insertion—default
â–
VM without removal of violations but with AIS insertion
â–
No violation monitoring CC mode with options for
—AIS insertion
— No AIS insertion.
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