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T320 SONET Clock Generator (SCG) Description


The SONET Clock Generators (SCGs) provide 19.44-MHz Stratum 3 clock signal for the SONET/SDH interfaces on the router. One SCG is shipped as part of the standard router configuration, but up to two SCGs can be installed to provide redundancy. SCGs are installed into the rear of the chassis in the slots labeled SCG0 and SCG1, which are located above the SIBs.

Backup SCGs are hot-removable and hot-insertable. Master and nonredundant SCGs are hot-pluggable.

The SCG with DB-9 ports (SCG-T320) is supported for Junos OS release 5.5 and later. Figure 1shows the SCG.

Figure 1: SCG with DB-9 ports
SCG with DB-9 ports

Each SCG consists of the following components:

  • 19.44-MHz Stratum 3 clock.

  • Field-programmable gate array (FPGA) that performs multiplexing of clock sources.

These components are located on the SCG faceplate:

  • Three LEDs—OK, FAIL, and MASTER, which display the status of the SCG.

  • SCG online/offline button.

  • Two external clock inputs labeled EXT CLK INPUT A and EXT CLK INPUT B..


    The external clock inputs are not supported.