Comtech EF Data CRS-200 REDUNDANCY SWITCH - Manual (Page 14)

CRS-200 COMTECH COMMUNICATIONS CORPORATION
CRS-200 REDUNDANCY SWITCH - OPERATIONS MANUAL PAGE 12
5 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 RS-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.
Each traffic modem is connected to the switch by its Traffic Modem Interface (TMI) card. The
same type of 25-pin cable used on the RMI should be used to connect the TMI to the traffic
modem’s primary data connector, again with fault status and RS-232 remote link included.
A second connector on the TMI (this one female) serves as the terrestrial data interface. The
TMI modules are designed so that they may be inserted or removed while the switch is
turned on, without causing interruptions to the data traffic. The TMIs also have a rear Online
LED, as well as a Bridged LED that also matches the front panel version. Any switch that is
ordered with fewer than 10 TMI cards will have blank plates installed in place of TMI cards
in the last unused slots.
The System Controller card is the heart of the switch, containing a 16-bit microcontroller,
flash-upgradable PROM and non-volatile memory. In addition to a 9-pin D-sub connector
(male) for remote communication between the switch and a PC in either RS-232 or RS-485
format, the System Controller also has a 25-pin connector (male) for interfacing the switch
to the Comtech IF transponder switch, a 25-pin connector (female) for switch and modem
alarm relay outputs and another 9-pin (female) connector that is reserved for a possible
auxiliary RS-485 remote link.