SRX3600 Services Gateway SRX Clustering Module
The SRX Clustering Module (SCM) is a card that you can install
in the services gateway to enable the dual control link feature for
chassis cluster supported in Junos OS Release 10.2 and later. You
install the SCM in the RE1
slot on the rear panel
of the services gateway. The SCM is shown in Figure 1.

The services gateway must be running Junos OS Release 10.2 or later to use the SCM. When running earlier Junos OS Releases, the services gateway does not properly recognize it.
For more information about configuring and managing chassis clusters, see the chapter “Chassis Cluster” in the Junos OS Security Configuration Guide.
For detailed information about the SCMs supported by the services
gateway, see the SRX1400, SRX3400, and SRX3600 Services Gateway Module Guide