RFC-1 Basic Operation page 5.4
5.4 Alarm System
The RFC-1 can monitor up to eight channels for abnormal telemetry conditions. If an out-of-tolerance condition is
detected, the system will call up to four telephone numbers to notify an operator of the condition. In basic operation,
the RFC-1 calls an operator but it does not attempt to correct the situation without user intervention.
5.4.1 How the Alarm System Works
After the alarm channels have been setup, the RFC-1 compares the current telemetry reading on the channel against
the alarm limits. As long as all systems are operating normally, the telemetry readings should stay within limits. If the
reading is outside of the programmed limits, the channel is technically in an alarm state. However, if the comparison
stopped there, it would be impossible to shut down a transmitter on purpose without generating an alarm.
To avoid that problem, the RFC-1 makes a reference scan at the end of every call, both local and remote. The idea
is that at the end of a call the systems are in a known state and the resulting telemetry conditions are acceptable.
The conditions at that time determine what alarms are armed. If an alarm channel is out of tolerance during the
reference scan, the alarm does not arm on that channel. The telemetry reading must be within the alarm limits at the
end of a call for the alarm on that channel to arm.
All alarms are disabled temporarily when the RFC-1 is online with an operator. Using the RFC-1 to adjust a device
out of limits does not generate an alarm. Likewise, no alarm occurs if a device goes out of limits by itself while a user
is connected.
When an alarm condition is detected, the RFC-1 begins making telephone calls to alert personnel of the condition. It
calls each number and says, “This is RFC-1/B. Telemetry alarm. Channel number,” followed by the number of the
channel that caused the alarm. Then it gives the channel reading at the time of the alarm. Earlier versions of the
RFC-1 gave a less detailed alarm message providing only the site ID and the number of the channel that failed.
Pressing any key interrupts the alarm message and clears the alarm. No more calls will be made for that alarm.
When a user has cleared an alarm, minimal access to the system is granted. Telemetry channels may be polled to
determine current system conditions. The system is still secure because control access has not been granted. If a
control function is activated, the control security code will be requested. The RFC-1 disconnects if the user does not
enter the correct security code.
The alarm call lasts for one minute if a user does not press a key to clear the alarm. The RFC-1 waits one minute
before placing the next call. This provides an opportunity for personnel to contact the RFC-1 and correct the
situation. If a user does not clear the alarm, the call sequence terminates after three call attempts to each number.
If a user clears the alarm, new reference readings are taken when the call ends. The user must adjust the offending
channel back into limits to re-arm the alarm on that channel. If the dialing sequence goes to completion without user
intervention, new reference readings are taken at the end of the sequence. This stops the RFC-1 from dialing
indefinitely for a single alarm.
5.4.2 Alarm System Setup
Three items must be programmed to use the alarm system in the RFC-1.
1. The channel numbers of the telemetry channels to monitor and appropriate upper and lower limits
2. Telephone numbers to call when the alarm sequence triggers—up the four telephone numbers
3. The telemetry alarm system must be enabled using the command 82
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