1022410 – 0001 Rev. 2
UMOD hardware theory of operation 3–37
The 9100 UMOD provides an optional redundancy feature that
allows one UMOD motherboard to be reserved as a spare for n
operational UMODs (where n is selected from 1 through 8). This
feature enables the user to avoid communications disruptions
caused by the failure of a UMOD.
The spare UMOD maintains a copy of the operating configuration
for each of the online (primary) UMODs over which it has control.
This is accomplished by polling all of the primary UMODs in the
redundant domain.
A failure is signalled to the redundant UMODs when a hardware
line is set to a failed state. The redundant UMOD motherboard
then switches the user terrestrial interface lines to itself, and
begins operating in whatever mode the primary UMOD was in
previously.
The redundant modem also polls each of the primary UMODs for
their status. Status indications of an ongoing or incipient failure in
a primary UMOD is also sufficient for the redundant UMOD to
switch in.
Two 1-PAK chassis may be set up to be 1:1 redundant (see
figure 3-21). A redundancy cable connects the redundant 1-PAK
chassis to the primary 1-PAK chassis (a multidrop cable is also
connected between the chassis).
Figure 3-21
1-PAK chassis 1:1 redundancy
MULTIDROP
TERRESTRIAL
DATA
M&C TERMINAL
ȍ
B
70 MHz
REDUNDANCY
CABLE
PRIMARY UMOD (1-PAK)
REDUNDANT UMOD (1-PAK)
CABLE
DATA
EQUIPMENT
3.5
Redundancy option
Redundancy using a
1-PAK chassis
