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Circuit Pack Descriptions
Issue 3 June 2001
7-87
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:
■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.
Control Circuitry 7
TheBBG19DS3circuitpackinterfaceswiththeSYSCTLviatheintra-shelf
control bus. The BBG19 DS3 provides maintenance elements for reporting the
status of the circuit pack, status of the incoming STS-1 and DS3 signals, as well
as the circuit pack inventory information (
CLEI
code, date of manufacture, etc.).
These maintenance elements are used by the SYSCTL for fault detection and
isolation. Conversely, the BBG19 DS3 responds to control signals from the
SYSCTL (such as active and fault LED controls).
Timing Circuitry 7
The BBG19 DS3 derives its timing information from the recovered DS3 clock from
the data services device incoming signal. In the transmit direction, a 44.736 MHz
clock is recovered from the incoming DS3 signal and is used to recover DS3 data.
In the receive direction, a smoothed 44.736 MHz clock is generated by a phase-
locked loop to accompany the DS3 signal extracted from the STS-1 payload.
In addition to the recovered DS3 clock, the BBG19 DS3 circuit pack requires
STS-1 timing supplied, via the circuit pack edge connector, from the backplane.
Locked DS3 Circuitry 7
The DDM-2000 OC-3 accepts two BBG19s installed side-by-side in a dual 0x1
configuration. This configuration allows for efficient bandwidth utilization in the
network for data services traffic. Each DS3 is assigned to both rotations of the ring
using the same STS-1 time slot. This dual 0x1 interface also provides route
diversity for point to multi-point interconnectivity and route restoration to data
networking devices utilizing the BBG19s for access to the SONET network.
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