• Replacing a T640 Craft Interface on page 265
T640 SONET Clock Generators (SCGs) 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 upper rear of the chassis in the slots labeled SCG0 and SCG1.
Backup SCGs are hot-removable and hot-insertable. Master and nonredundant SCGs
are hot-pluggable.
The router supports the SCGs in Table 9 on page 27.
NOTE: Redundant SCGs must be the same model number, except during
upgrade.
Table 9: Supported Power Supplies
FirstSupportedJunos OS
ReleaseModel NumberName
5.3SCG-TSCG with DB-9 ports
(Figure 12 on page 27)
10.4SCG-T-ECSCG with RJ-48 ports
(Figure 13 on page 28)
Figure 12: SCG with DB-9 Ports
27Copyright © 2017, Juniper Networks, Inc.
Chapter 3: Chassis Components and Descriptions
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