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Circuit Pack Descriptions
Issue 3 June 2001
7-73
Power Circuitry 7
The BBG4/BBG4B DS3 circuit pack receives two sources of −48 volts that are in
turn diode ORed, fused, and filtered before conversion to +5 volts to power the
rest of the circuit pack. A failure of the fuse or converter causes the red FAULT
LED to light.
BBG4/BBG4B DS3 Quick Reference Summary 7
Transmit Functions 7
The BBG4/BBG4B DS3 transmit functions are as follows:
â– Receives a B3ZS-encoded DS3 signal from a DSX-3
â– Recovers DS3 clock and NRZ data
â– Optionally checks and/or corrects P-bit parity errors
â– Synchronizes the data signal to STS-1 signal rate
â– Inserts STS-1 path overhead
â– Provides the STS-1 signal to the OLIU circuit packs.
Receive Functions 7
The following receive functions are performed by the BBG4/BBG4B DS3 circuit
pack:
â– Desynchronizes the incoming STS-1 signal
â– Terminates the STS-1 path
â– Optionally checks and/or corrects P-bit parity errors
â– B3ZS encodes the outgoing DS3 signal
â– Pre-equalizes the DS3 signal (with LBO) and transmits it to a DSX-3.
Control Functions 7
The major control functions are as follows:
â– Protection switching for BBG4/BBG4B DS3 circuit packs
â– STS-1 path overhead processing
â– Internal fault detection
â– Inventory information (
CLEI
code, date of manufacture, etc.).