T640 Sonet Clock Generators (Scgs) Overview; T640 Standard Sonet Clock Generators (Scgs) Description; Figure 22: Scg - Juniper T640 Hardware Manual

T640 Core Router Hardware Guide
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T640 SONET Clock Generators (SCGs) Overview

T640 Standard SONET Clock Generators (SCGs) Description

40
Table 10: T-CB LEDs (continued)
Label Color
Green
OK
T640 Chassis Description on page 13
Replacing a T640 T-CB on page 201
Maintaining the T640 T-CBs on page 149
T640 Standard SONET Clock Generators (SCGs) Description on page 40
T640 SONET Clock Generators (SCGs) LEDs on page 41
The SONET Clock Generators (SCGs) provide 19.44-MHz Stratum 3 clock signal for the
SONET/SDH interfaces on the router (see Figure 22 on page 40).
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
Backup SCGs are hot-removable and hot-insertable. Master and nonredundant SCGs
are hot-pluggable.

Figure 22: SCG

Each standard SCG consists of the following components:
19.44-MHz Stratum 3 clock.
Field-programmable gate array (FPGA) that performs multiplexing of clock sources.
Three LEDs, located on the SCG faceplate, that display the status of the SCG.
SCG online/offline button, located on the SCG faceplate.
Two external clock inputs.
State Description
On steadily T-CB is online and is functioning normally.
Blinking T-CB is powering up, but not online.
SCG1 .
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