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CRS-180 70/140 MHz IF 1:1 Redundancy Switch
Introduction
1.1.2
Antenna Side Connectors
Two 50Ω female BNC connectors on the antenna side of the CRS‐180 70/140 MHz IF Switch
module provide the coaxial cable connections to the outdoor transmit and receive equipment.
Refer to Figure 1‐3 and the accompanying table for details.
Figure 1-3. CRS-180 – Antenna Side Connectors and Ground Lug
1.2
Functional Description
The CRS‐180 70/140 MHz IF 1:1 Redundancy Switch module performs the Tx and Rx coaxial
switching required for redundant modem operation with an outdoor BUC and LNB.
1.2.1
Operation with CDM-625/750/570/700/710/710G
The CRS‐180 is configured with two modems to form a complete 1:1 redundant modem system.
Within the CRS‐180, a redundancy controller continually monitors the status of faults for both
modems to determine which modem should be Online and Offline. The control cables between
the modems and the CRS‐180 include four signal groups:
•
First, serial full‐duplex communication lines are routed from one modem to the other
modem via the CRS‐180. Using these lines, this Online modem can interrogate the
Offline modem at regular intervals to determine its configuration. If a difference in
configuration is detected, the Online modem will reconfigure the Offline modem so that
the configurations are always synchronized. This process is entirely automatic – if the
Offline modem is replaced, it does not have to be manually reprogrammed to match the
Online modem.
•
Second, the Modem's Unit, Tx and Rx faults signals from both modems are routed to the
CRS‐180. This allows the redundancy controller to always know the health status of both
modems.
Name
Ref Des
RX
J7
TX
J8
Connector Type
BNC
BNC
1–3
Revision 8
MN/CRS180.IOM
Function
IF Input
IF Output
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