Figure 2-2 - Modem Connections For 1:1 Redundancy - Datum Systems PSM-500 Installation And Operation Manual

M500 vsat/scpc satellite modem

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Table of Contents

Installation

Note: The two modems should be at the same firmware revision for proper redundant operation.

The two modems operate in a "non-priority" redundancy mode, that is, no modem is specified as

"primary", or having preference when both modems are operational. The first modem turned on

assumes a non-redundancy mode until the second connected unit is powered up. The on-line

unit can be set to send its configuration information to a second unit via the front panel. The

modems will remain in this state, constantly sending status information back and forth until one

unit indicates a failure. If that modem is currently on line, it is switched off-line and the alternate

unit is switch on.

The modem is also capable of operating in 1:N and M:N redundancy switching schemes. The

necessary connections to monitor and control switching are available on the data connector itself

in the form of the modulator and demodulator fault outputs and the auxiliary RS-232 control port.

The alarm outputs are also available. The other facility provided to aid in these redundancy

schemes is the ability to save and recall configuration information. Thus a back-up modem can

obtain and save the configurations from 8 other modems and switch immediately to the

necessary parameters to replace any of those units by simply recalling that unit's stored

configuration. In addition, the programmable interface and common physical data connector

allows different interface protocols between the primary modems.

A diagram of the connections required for installing 1:1 redundancy is shown in the figure below.

Data "Y" Cable