Operating instructions

RCS20 M:N Redundancy Switch Installation
TM056 - Rev. 2.3 2-9
Figure 2-7. Complete System Interconnection and Cabling Information for System
Configuration
2.5.2 Reference Distribution Module
The Reference Distribution Module (RDM) is an optional RCU20 expansion card that is used to
buffer and distribute earth station frequency reference(s) to the external reference input of modems
that are connected to an RCS20. The RDM automatically switches between EXT A, EXT B or Internal
References based upon onboard Clock Activity Detect circuits.
The RDM is illustrated in Figure 2-8. There are six BNC-type connectors on the RDM. The function
of the individual connectors is as follows:
J1 EXTA IN Primary Internal Reference Input
J2 EXTB IN Secondary Internal Reference Input
J3 OUT 1 Reference Output 1
J4 OUT 2 Reference Output 2
J5 OUT 3 Reference Output 3
J6 OUT 4 Reference Output 4
The RDM also contains an internal reference in two options; High-stability or normal. These options
and the electrical specifications for the above connectors are shown below.