T320 Sonet Clock Generator (Scg) Description; Figure 9: Scg With Db-9 Ports - Juniper Core Router T Series Hardware Manual

T320 SONET Clock Generator (SCG) Description

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Copyright © 2018, Juniper Networks, Inc.
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
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 9 on page 19shows the SCG.

Figure 9: 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
SCG online/offline button.
Two external clock inputs labeled
NOTE: The external clock inputs are not supported.
T320 SCG LEDs on page 20
Maintaining the T320 SCGs on page 273
Replacing a T320 SCG on page 186
T320 Component Serial Number Label Locations on page 312
Chapter 3: Chassis Components and Descriptions
SCG0
MASTER , which display the status of the SCG.
and
EXT CLK INPUT A
and , which are located
SCG1
..
EXT CLK INPUT B
19