Circuit Pack Descriptions
7-38 Issue 8.0 July 2002
Control Circuitry 7
The board controller circuit controls all the circuit pack activities. The board
controller circuit interfaces with the LNCTL circuit pack using the board controller
local area network (BCLAN). The DS3 circuit pack reports the status of the circuit
pack and the incoming DS3 and 155.52 Mb/s signals, as well as the circuit pack
inventory information (CLEI code, serial number, etc.). The LNCTL circuit pack
uses the status information for fault detection and isolation. The DS3 circuit pack
also responds to control signals from the LNCTL circuit pack.
Timing Circuitry 7
The DS3 circuit pack accepts two 155.52 MHz clock signals from the Timing
Generator, Stratum 3 - DS1 [TG3 (DS1)] circuit packs (primary and secondary).
During normal operation, the board controller selects the clock signal that is used.
The selected clock signal (155.52 MHz) is connected to the byte
multiplexer/demultiplexer that provides a divide-by-3 circuit. The divide-by-3
circuit generates a 51.84 MHz signal and sends it to an 8 KHz synchronization
generator that is part of the high speed interface. The 8 KHz synchronization
signal and 51.84 MHz clock signals are connected to each DS3/STS-1
synchronizer/desynchronizer.
Protection Circuitry 7
Low Speed Interface Protection. 7Optional 1xM (M≤16) revertive DS3 circuit pack
protection is provided. A DS3 protection bus is implemented with on-board relays
on the DSX-3 side and with selectors at the 155.52 Mb/s level on the service and
protection OC48 Transmitter and OC48 Receiver circuit packs. The Low Speed
Switch (LSSW) circuit pack provides power to these relays and controls their
operation. If the +5 volt power on the DS3 circuit pack fails, the relays are still
operational and controlled by the LSSW and LNCTL circuit packs. If the LNCTL
circuit pack is removed, the relays will remain in their current state. Shorting
contacts are provided in the DS3 circuit pack backplane connector so that when
the circuit pack is removed, the DSX-3 cables short through to the LSSW circuit
packs for routing to the protection DS3 circuit pack. When the DS3 circuit pack is
reinserted, the relays are in the protection state until the LNCTL circuit pack
determines that the circuit pack is good.
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