Comtech EF Data CRS-200 - Manual (Page 21)

Rev. 1 3–1
3
Chapter 3.
FUNCTIONAL DESCRIPTION
The CRS-200 is a 1-for-N redundancy controller, meaning that a single redundant
modem (referred to as an RM) can be employed as a backup in the event of a failure to
any one of up to 10 traffic modems (referred to as a TM). An overall system is shown in
Figure 3. The front panel includes system status LEDs that indicate the current fault
status of all the modems connected to the switch. In addition, there are LEDs for the
modems’ online status and, for the traffic modems, an indication of which modem is
currently being “bridged” by the redundant modem. This means that the redundant
modem has been programmed to match the configuration of that selected traffic modem,
and is being fed with a copy of the traffic signals that the TM sees.
In addition to the main chassis, there are 4 different types of plug-in units, all of which
are fastened at the rear of the chassis using hand-tightened captive screws. These are the
Redundant Modem Interface (CRS-210), of which one is required in the leftmost slot
while looking at the rear of the chassis; the Traffic Modem Interface (CRS-220), of
which one is needed for each traffic modem to be used and can occupy any of the other
ten slots; the System Controller (CRS-230), of which one is required; and the Power
Supply Module (CRS-240), for which 2 slots are provided so that the switch can operate
with either/both installed.
The Redundant Modem Interface (RMI) card has a single 25-pin male D-sub connector
that is attached to the redundant modem’s primary data connector with a shielded cable.
This connection between the RMI and the redundant modem includes fault relay status
from the modem to the switch as well as an EIA--232 remote control link, so that no
other interconnections are required. Transmit terrestrial signals normally sent to the
bridged traffic modem are also routed to the redundant modem through this connection.
When the redundant modem is put online, all terrestrial signals from the redundant
modem replace those of the traffic modem that was taken offline. An online LED is also
present that matches the corresponding Redundant Modem Online indicator on the
switch’s front panel.