Comtech EF Data CDM-Qx, Installation And Operation Manual

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Chapter 10. REDUNDANCY
Redundancy is built into the modem and can be enabled using the FAST optioning.
Redundancy can be selected so as to perform back up in the following scenarios:
•
1:1 (one modulator for one modulator), (one demodulator for one demodulator),
(one modem for one modem)
•
1:2 (one modulator for two modulators), (one demodulator for two demodulators)
•
1:3 (one modulator for three modulators), (one demodulator for three demodulators)
Location of the modules in the chassis is critical for correct operation of the redundancy
functions. When single modules are being backed up, the backup unit must be located in
the lower right-hand slot as viewed from the rear. When modules grouped as modems
are being configured as redundant the backup modem has to be located in the right hand
column of slots, with the modulator on top.
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, removing four screws,
replacing the interface, and reinstalling the four screws.
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