Comtech EF Data CRS-200 - Manual (Page 24)

Functional Description CRS-200 Redundancy Switch
3–4 Rev. 1
Figure 3-2 Data Switching Details
A CRS-240 Power Supply Module is installed in each side of the chassis. If one module
is removed while power is on, the system continues to operate with no disturbance. This
allows servicing of a module without interruption. The controller monitors the +5V,
+12V and –12V supplies of each module separately, and any fault reported on either
module can be masked if the user chooses to operate without a backup in place. Module
A is on the right and Module B is on the left as viewed from the rear of the chassis.
The microcontroller in the CRS-200 continuously scans the system to gather information.
This information is then used to determine if action needs to be taken. Every second,
three status checks are performed. First, all 11 modem interface positions are checked in
succession for the presence of an interface card and, if present, all three modem alarm
relay conditions are checked. If a modem interface is present but no modem is connected
with the 25-pin cable, all three fault indicator LEDs on the front panel will show the
faulted state. Unmasked faults are logged.
Second, the switch checks itself for faults. These consist of either power supply faults or
a failure to communicate remotely with the redundant modem, and are also logged if
unmasked. The outputs of both power supplies are monitored for both overvoltage and
undervoltage conditions, but only one supply may have its faults masked at a time. A
remote communication fault with the redundant modem may not be masked, since the