RFC-1 Basic Operation page 5.6
5.4.6 Enabling / Disabling the Power Failure Alarm
The RFC-1 can alert an operator of an AC power failure at the remote site. In most cases, this alarm triggers when
AC power returns. The RFC-1 uses the same dialing procedure as it does for telemetry alarms as described in
section 5.4.1 but the message delivered is “This is RFC-1/B. Power failure.” An operator clears this alarm just like
any other alarm.
The command to enable or disable the power failure alarm is 82. Set the value to 0 to disable the power failure alarm
system or 1 to enable it. The power failure alarm is disabled when the RFC-1 ships from the factory.
1. Enter the command for the power failure alarm: 81
2. The RFC-1 reads the current setting for the power failure alarm.
3. At the prompt, press the # key to reprogram the power failure alarm: #
4. At the prompt, enter a 1 to enable the power failure alarm or a 0 to disable it: 1
5. The RFC-1 responds with “OK”, the procedure is complete
At least one telephone number must be programmed for the power failure alarm to be effective. The procedure for
storing telephone numbers is described in section 5.4.4.
More recent hardware versions of the RFC-1 have the ability to detect the loss of AC power. When the power failure
alarm is enabled in a system with this capability, the system will trigger an alarm when loss of AC power is detected.
This allows the system to generate an alarm while operating from a DC supply, such as a backup battery.
When the RFC-1 places telephone calls as a result of the power failure alarm it delivers a message including the site
identification phrase and the alarm message “AC power failure.”
The internal power failure alarms are ineffective when a UPS is used because the RFC-1 does not lose power. To
detect loss of AC power at the site, connect 3-6 volt, unregulated DC wall-plug transformer to an unused telemetry
channel. Calibrate and program the channel to read 120 volts. The system is now able to monitor AC line power.
Program a telemetry alarm on this channel to have the system contact station personnel when power fails.
5.4.7 System Limitations
The RFC-1 has no way of recognizing that changes made from the front panel of the transmitter (or by another
remote control connected in parallel) are being performed by an operator. If a device that is monitored by the RFC-1
is adjusted out of tolerance and the RFC-1 is not responsible for the adjustment, an alarm will be triggered.
If multiple alarms trigger at once, for instance if a site loses AC power and everything shuts down at once, only one
alarm triggers. Which alarm triggers is determined by where the RFC-1 is in the scanning sequence when the failure
occurs. The system relies on the operator to poll the system and determine the nature and degree of failure.
The alarm system is not instantaneous. Alarm channels are scanned at a rate of one channel every 10 seconds after
the initial reference scan completes. In the worst case, it can take up to 80 seconds before an alarm is recognized.
In reality, alarms are nearly always recognized much quicker than that. If not all alarms are used, the worst-case
scenario is less than 80 seconds. The worst case is the number of alarms used multiplied by 10 seconds.
The system stops scanning when alarm triggers. It is possible for the telemetry channel that caused an alarm to
return to normal before an operator is reached. The system does not automatically terminate the alarm.
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