CRS-300 1:10 Redundancy Switch MN/CRS300.IOM
Introduction Revision 19
1–3
If you use the G.703 interfaces, you will need only one additional cable for each modem.
• When you use the CDM-Qx/QxL
modems – You will need to connect an additional EIA-485
multi-drop cable from the Switch to all modems. This cable enables remote control interface
capability.
• For EIA-232/EIA-485 M&C User connections – A direct user-to-modem serial EIA-232/-485
communication connection is not permissible when connected to the Switch. You must
instead connect to the DB-9 "Remote" connector on the CRS-230 System Controller that is
installed on the Switch.
Appendix C. ADDRESSING SCHEME INFORMATION
TMI Monitoring – Terrestrial user clock and data signals to and from a Traffic Modem are routed
through a TMI via a set of relays. This is arranged so that the de-energized (unpowered) state
connects the data signals directly through to the Traffic Modem. If the power supplies to the
system are lost, or if a traffic-carrying TMI is removed, no interruption of the traffic occurs. It
should also be noted that, in normal circumstances where the Redundant Modem is not in
service, no data is carried through the CRS-300 backplane – all data is routed via the TMI.
CRS-280/280L Option –
Figure 1-2 in Sect. 1.1.2 shows an operational schematic for the
optional CRS-280/280L interface:
• The CRS-280 (70/140 MHz) Switch is necessary when one or more modems within the
redundancy system connect to more than one up/down converter. This occurs when the
modems connect to more than one transponder on the same antenna polarization, or when
modem redundancy needs to span two or more polarizations or antennas.
• The CRS-280L (L-Band) Switch is necessary when one or more modems within the
redundancy system connect to the other polarization of the antenna or to multiple
antennas.
The system may forego using the CRS-280/280L and, in its place, passively combine or split the
modulator outputs and demodulator inputs when the entire group of modems is connected to
the same up/down converter. In these applications, the CRS-300 mutes the faulted modem’s Tx
carrier and enables the standby unit’s carrier.
Comtech EF Data CRS-280L 1:N Redundancy Switch Installation and Operation
Manual (CEFD P/N MN/CRS280L.IOM)
CRS-350 Option – Figure 1-24 through Figure 1-26 in Sect. 1.4 show details of the CRS-350
ESC Switch. You may add this unit if you require
protection of the IDR overhead signals
(backward alarms, audio ESC, data ESC, etc.).
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