Comtech EF Data CRS-170 - Manual (Page 23)

CRS-170 1:1 Redundancy Switch Revision 1
Installation and Operations Manual MN/CRS170.IOM
25
Fault status information is fed from each of the two modems via the Data Interface
connector. The Controller State Machine in the CRS-150 decides, based on the fault
status, whether the ‘A’ or ‘B’ unit is to be the online unit. It will assert a control signal to
the standby unit, which mutes its Tx IF carrier, and simultaneously indicates to the
microcontroller within the standby unit that the unit is no longer ‘online’. Consequently,
the ‘online’ LED on the front panel of the standby modem is extinguished, and the
standby status is also reported over the remote control bus so an external M&C system
can determine the state of the redundancy system. At the same time, a green LED will
illuminate on the front of the CRS-150 to indicate whether the ‘A’ or ‘B’ unit is online,
and a green LED on the antenna side of the CRS-170 will indicate the same status.
3.2 O
PERATION WITH
SDM-300L3
AND
SMS-301
The SMS-301 is modified from the standard version that operates with 70/140 MHz IF
SDM-300A modems. The BNC IF connectors are removed since the connectors and
internal switching are not suitable for L-Band operation. Signals on the Status/Faults
connector (J14) are modified to provide +12VDC power output and A/B switch control
outputs to the CRS-170. The SMS-301 has its own redundant power supplies, so the
CRS-170 receives redundant power.
Operation here is similar to operation with two CDM-600L modems and a CRS-150
switch. The SMS-301 operates as the principal switch and controller with the CRS-170
providing the required switching for L-Band signals, references, and power supplies that
the SMS-301 cannot handle. The SMS-301 connects to two modems, an online unit, and
a standby unit, monitors the fault status of these two units, and controls the routing of
data to and from the two units. IF signals, 10MHz reference signals, DC power for the
BUC and LNB, and FSK signaling to the BUC are switched in the CRS-170 under
control of the SMS-301. In the case of an equipment failure, switching automatically
takes place to protect the traffic circuit. Consult the SMS-301 manual for detailed
information on operation of the SMS-301. All operation as a 70/140 MHz modem switch
applies except that the RF switching is done in the CRS-170.
For operation with the SNM-1001L or SNM-1010L, refer to sections pertaining to the
SDM-300L3.