Comtech EF Data CDM-570A - Manual (Page 582)

CDM-570A/570AL Satellite Modem with Optional Packet Processor MN-CDM570A
Appendix N Revision 2
N–4
N.3 CRS-XXX 1:1 Redundancy Switch Functional Description
N.3.1 CRS-180 70/140 MHz 1:1 Redundancy Switch
See the CRS-180 70/140 MHz 1:1 Redundancy Switch Installation and Operation
Manual (CEFD P/N MN/CRS180.IOM) for detailed information on CRS-180
operation.
The CRS-180 70/140 MHz 1:1 Redundancy Switch performs the transmit and receive coaxial
switching required for redundant modem operation. It switches both the Tx and Rx coaxial
cables simultaneously.
Select Unit Faults only, Unit Faults or Receive Traffic Faults, or Unit Faults or Transmit Traffic
Faults, or all three for the switchover criteria with the two switches on top of the unit. This
selection provides a great deal of flexibility in the operation of the switch. Green LEDs on the
antenna side of the CRS-180 indicate which modem is online.
The control cable from each modem to the CRS-180 also includes +12V power to operate the
CRS-180. Power from both modems is diode OR’ed so that the switch remains active if power is
lost from one of the modems.
The CRS-180 provides IF redundancy. On the Tx side, it switches the Tx IF signal. The Rx IF signal
from the RF equipment is split in a power divider to continuously drive both the online and
offline demodulator. The offline demodulator can then maintain lock so that it is ready to
quickly assume online status for receive traffic when a switchover is required.
N.3.2 CRS-170A L-Band 1:1 Redundancy Switch
See the CRS-170A L-Band 1:1 Redundancy Switch Installation and Operation
Manual (CEFD P/N MN/CRS170A.IOM) for detailed information on CRS-170A
operation.
The CRS-170A L-Band 1:1 Redundancy Switch performs the Tx and Rx coaxial switching required
for redundant modem operation with an outdoor BUC and LNB. It switches all of the BUC and
LNB interface signals that are multiplexed onto the Tx and Rx coaxial cables:
• Tx and Rx L-Band signals
• 10 MHz reference to BUC and LNB
• DC Power to BUC and LNB
• FSK signaling to the BUC
Select Unit Faults only, Unit Faults or Receive Traffic Faults, or Unit Faults or Transmit Traffic
Faults, or all three for the switchover criteria. This selection provides a great deal of flexibility in
the operation of the switch. Green LEDs on the antenna side of the CRS-170A indicate which
modem is online.