Comtech EF Data OMS11 - Manual (Page 18)

OMS11 1:1 Redundancy Switch Theory of Operation
TM133 – Rev. 1.1 2-3
2.2 OMS11 Major Assemblies
The OMS11 Redundancy Control Unit contains the modules that control and monitor the
operation of the 1:1 Switch system. The 1:1 Switch is composed of the following major
assemblies and components:
Main Switch Board
Waveguide Switch Board
Front Panel
Dual (Redundant) Power Supplies
2.2.1 Main Switch Board
The Main Switch Board contains the OMS11 1:1 Switch Intelligence and Memory Circuitry and all
switching circuitry. The microprocessor controls and coordinates all of the major functions of the
Switch and performs all necessary calculations. The non-volatile system memory on the board
stores the switching parameter settings for each modem channel. Control and data signals are
routed to the appropriate devices in the system through various latches and transceivers that are
controlled by the microprocessor.
2.2.2 Front Panel
The Front Panel contains the LED Indicators and the pushbutton switches needed to control and
operate the OMS11. Refer to Figure 3.0 for a description of Front Panel Indicators.
2.2.3 Redundant Power Supplies
The 1:1 Switch comes equipped with two fully redundant internal power supplies (PS1 and PS2)
that supplies power to the switch and external switching components. Each supply is fully
independent of the other, including their source of AC/DC power and fusing. The Switch can
remain fully operational as long as it is supplied with a source of voltage from either power
supply.
2.3 OMS11 General Operation
2.3.1 Data Signals
Modem data signals are backed-up through a passive switching system. Signals that are
required to maintain the modem in off-line (hot-standby) are buffered by appropriate circuitry to
minimize loading on incoming signals.
2.3.2 Backup
If an online Modem fault is sensed, and the off-line Modem is in a non-faulted state, the OMS11
will switch to the Modem without the fault. The Fault Signal has a small debounce delay to
prevent false triggering. If the faulted Modem has its fault cleared, it stays off-line unless the
other MODEM has subsequently faulted.
2.3.3 Fail-Safe
If the OMS11 has a non-recoverable internal fault, the switch will revert back to Modem A, the
Switch Fault LED is illuminated, and the Switch Fault Relay switches to a faulted state.