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Operation
PSM-500/500L/500LT SCPC Satellite Modem
The analog output presented at the rear panel Alarm connector J5 has a 1kΩ output impedance,
protecting the driver circuitry from shorts.
3.13 Storing and Recalling Configuration
The PSM-500 modem has a built-in function allowing the operator to store the current complete
configuration in one of 8 numbered locations.
Any stored configuration can then be recalled, including one permanent configuration called
"Factory" which is a set of default configurations.
3.14 Automatic Configuration Recovery - ACR
The PSM-500 modem has an additional feature related to the ability to store and recall
configurations. Any or all of the 8 configurations can be set to be automatically recalled in the
event of receive carrier loss for more than a specified number of seconds. This automatic recall is
termed "Restore" on the control options. Each configuration has an associated time parameter
that is normally set to a 0 (zero) value. When any other value up to 14,400 seconds is placed in
this parameter then that configuration is recalled if the current configuration results in a loss of
carrier for more than the specified number of seconds.
The automatic configuration recovery feature, or ACR is also commonly used with the ability to
turn the carrier off after loss of receive carrier.
A feature added in version 0.52 of the modem firmware allows the power up behavior of the
modem to be selected as either "Last" or recalling one of the 8 stored configurations. Last is the
normal previous mode where the modem powers up using the last settings. Recall 1..8 will recall
any stored configuration on power up. The default stored in each configuration is the factory
settings.
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Note: The ACR is not available when the modem is operating in a redundancy mode.
Several examples more clearly illustrate the use and operation of the automatic configuration
recovery (ACR).
Consider a demand access type system where modems not currently in use are intended to be
placed at a "home" location. This would consist of mainly a receive IF frequency and data rate
where the modem could receive assignment information. By storing the necessary parameters for
the home location in configuration #1, and setting the configuration #1 time to 10 seconds, the
modem will return to home whenever no carrier is received for 10 seconds. Then upon receiving
an assignment, going to the new assigned set-up, and passing data traffic the link "tear-down"
only requires removing the inbound carrier. 10 seconds later the modem will return to the home
location awaiting another assignment.
Consider a simpler system that uses the multiplexer option to remotely program a far end
modem. This ability is only available via remote control, not the front panel. If a remote
unattended modem is erroneously commanded to a location and does not find the carrier then it
may be impossible to "re-acquire" that modem, necessitating a technician to visit that site. By first
storing the current configuration in one available location, and then setting the time to perhaps 30
seconds (all over the link itself) for that configuration then the remote modem can safely be sent
a command to change frequency (for example) knowing that if the modem does not lock up to a
receive carrier in 30 seconds it will return to the current configuration.
Multiple configurations can have time settings associated with them. The result is that each
configuration will be tried in turn until a carrier is found and locked. Upon losing the receive
carrier again the modem will restart the configuration sequence beginning with the lowest
numbered configuration having an associated non-zero time. The sequence is repeating with the
highest configuration with a non-zero time "wrapping" around to the lowest.
Page 3-40
PSM-500/500L/500LT - Rev. 0.91
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