Chapter 11. Redundancy; Figure 11-1. Cdm-Qx/Qxl Chassis Rear Panel Schematic - Comtech EF Data CDM-Qx Installation And Operation Manual

Chapter 11. REDUNDANCY

Redundancy is built into the modem and can be enabled via the FAST option activation
procedure. Redundancy can be selected so as to perform backup in the following scenarios:
•
1:1 Redundancy, meaning:
One modulator for one modulator;
One demodulator for one demodulator;
One modem for one modem.
•
1:2 Redundancy, meaning:
One modulator for two modulators;
One demodulator for two demodulators.
•
1:3 Redundancy, meaning:
One modulator for three modulators;
One demodulator for three demodulators.
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Figure 11-1. CDM-Qx/QxL Chassis Rear Panel Schematic

Location of the modules in the chassis is critical for correct operation of the redundancy functions.
Using the Figure 11-1 schematic for reference, note the following:
•
When single modules are backed up, the backup unit must be located in the lower right-
hand slot (Slot#4) as viewed from the rear.
•
When modules grouped as a modem are configured as redundant, the backup modem has to
be located in the right-hand column of slots (Slot#3 and Slot#4), with the modulator
module on top (Slot#3).
If a 1:1 modulator and a 1:1 demodulator configuration is desired, group the boards as modems and
set up as described above.
Redundancy switching is implemented after the data interface. This means that the unit or units
designated as the backups do not require a data interface that matches the online units or an
interface at all to operate as a backup.
Note: CEFD recommends that at least one extra interface be purchased, so that if an interface
should fail in the field, that interface can be replaced. This is easily accomplished by removing the
modulator or demodulator module by loosening the captive thumbscrews keeping it in place, then
installing the new module into the desired chassis slot and hand-tightening its captive thumbscrews.
Slot 1
Slot 2
11–1
Slot 3
IF I/O
Slot 4