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    SCG Overview

    You monitor the SCGs to ensure that they provide a clock signal for the SONET/SDH interfaces on the router and that they select a clock signal from any FPC, or from the external clock inputs.

    The SCGs provide a 19.44-MHz Stratum 3 clock signal for the SONET/SDH interfaces on the router. The SCGs can also select a clock signal from any FPC, or from the external clock inputs (see Figure 1).

    Figure 1: SCG Component

    SCG Component

    Two SCGs are installed in the T320, T640, and the T1600 routers. The SCGs install into the upper rear of the chassis in the slots labeled SCG0 and SCG1.

    If both SCGs are installed and functioning normally, SCG0 is master and SCG1 is backup. Removing the backup SCG does not affect the functioning of the router or router. Taking the master SCG offline might result in a brief loss of SONET clock lock while the backup SCG becomes master.

    The SCGs are hot-pluggable.

    Figure 2 shows the location of the SCGs on the T320, T640, and T1600 router.

    Figure 2: T320, T640, and T1600 Router SCG Location

    T320, T640, and T1600
Router SCG Location

    Published: 2012-08-20