M7/M7L/M7LT Modular Satellite Modem Maintenance
M7/M7L/M7LT - Rev. 0.05 2-23
2.6. Redundancy Connection (Future Option)
Connection of two (2) M7 units in 1:1 redundancy is accomplished by using a special the data “Y”
cable specified in Appendix C - Cabling Specifications, an IF combiner, and IF splitter. The two
modems communicate with each other to determine the alarm status of each and force the “off-line”
unit’s data interface into an un-terminated condition. This allows both interfaces to receive incoming
data and clock signals, which are necessary to ascertain correct functioning. At the same time,
transmit and receive IF ports are also connected together through transmit and receive IF
combiner/splitter assemblies.
The major advantage to the built-in redundancy capability is its extreme low cost but there are
additional advantages.
The second (or back-up) unit is sent its full configuration from the on-line unit eliminating any
configuration errors
fully programmable alarm content that determines the switching criteria
The single point failure of the switch in a classic 1:1 redundancy scheme is eliminated
Operation of the 1:1 redundancy mode is described in Section 3.14
NOTE: The two modems should be at the same firmware revision for proper redundant operation.
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