Comtech EF Data DT-4500-A Series - Manual (Page 142)

DT-4500-A Series Downconverters Revision 0
Appendix B MN-DT4500A
B–2
B.2 Backup Downconverter
The "Daisy Chain" terminates in the backup downconverter. The backup downconverter has a
microprocessor, which performs fault detection, self-reconfiguration and the logical switching
functions. If the backup downconverter does not have a fault, it will assume the frequency and
attenuation of the faulted downconverter and compensate for the chain losses. This capability is
accomplished through the operation of the HSB and the online downconverter detachable
switch modules.
B.2.1 High Speed Bus (HSB)
In the "Daisy Chain" configuration, the backup downconverter communicates with the online
units through the HSB. The backup downconverter is able to detect faults and reconfigure itself
to replace the faulted downconverter. The HSB interface is also used in the backup
downconverter to monitor configuration changes made to an online downconverter. Changes in
frequency, gain, or polarity are immediately entered into the backup table as well as
information from new online units. The high-speed bus does not interfere with the remote serial
communication link access to any of the downconverters in the chain.
B.2.2 Detachable Modules
Comtech EF Data's downconverters are designed with a detachable Input/Output Module (IOM),
which contain the signal path connectors. The IOM is utilized for single thread operation, or for
testing of the unit.
For redundant "Daisy Chain" operations, the on-line downconverters are provided with a
detachable Receive Switch Module (RSM) replacing the IOM.
Refer to Chapter 3. REAR PANEL CONNECTORS, Sect. 3.2.2.2 for quick reference tables for the
modules available to both the DT-4500-A Series Downconverters and the UT-4500-A Series
Upconverters.
B.2.2.1 Downconverter Switching
The RSM contains IF switches for input/output looping of the signal. Options for the RSM include
SMA connectors for the RF Input signal, and 50 or 75Ω BNC connectors for the IF.