The AFS-3 Audio Failsafe can be used as an accessory to the RFC-1/B Remote Facilities Controller. In such an installation, the relay outputs of the AFS-3 are connected to an unused telemetry input of the RFC-1. Voltage must be applied to the relay contacts so that the RFC-1 can sense a status change. Fortunately, the AFS-3 has provisions for applying this voltage.
The procedure outlined below is not difficult and involves only low voltage circuits. However, high voltages are present in the transmitter environment and such circuits may be in the immediate vicinity or connected directly to the RFC-1. These high voltage circuits are capable of delivering a lethal shock! If you are not familiar with the transmitter or are not comfortable in the environment please do not continue with this procedure.
Applying voltage to the AFS-3 output relay contacts
Disconnect all connections to the AFS-3 before continuing. The jumpers that apply the voltage to the AFS-3 relay contacts are inside the AFS-3. They are accessed by releasing the two screws, removing the rear panel of the AFS-3 and sliding the PCB out of the chassis. Inside there is a jumper block with four positions (JP) labeled 1-4.
- Install a jumper at position JP4 to engage the +5VDC on the relay common pole.
- Install a jumper at position JP2 to have +5VDC present when audio is present, or
- Install a jumper at position JP3 to have +5VDC present when audio fails
Always install JP4 and install either JP2 or JP3. Remember which jumper you installed JP2 or JP3; it will be important in a few moments. Re-assemble the AFS-3 by sliding the PCB back into the chassis rails. Replace the rear panel and install the two screws that were removed earlier.
Connecting the failsafe output to the RFC-1/B telemetry input
In this step two wires will be connected from the AFS-3 relay output to an unused telemetry input on the RP-8 relay panel of the RFC-1/B system. This connection carries the +5VDC signal that allows the RFC-1 to sense the status of the AFS-3.
- Connect the AFS-3 relay COM terminal to the "+" telemetry input
- If JP2 was installed, connect the AFS-3 relay NO terminal to the "-" telemetry input
- If JP3 was installed, connect the AFS-3 relay NC terminal to the "-" telemetry input
Power the devices and apply appropriate input signals. The telemetry channel of the RFC-1 may require calibration. Go online with the RFC-1 and select the channel to which the AFS-3 has been connected.
If JP2 was installed above, the RFC-1 should report "status on" when audio is present and "status off" when it is not. In this case the voltage indicates presence of audio.
If JP3 was installed above, the RFC-1 should report "status off" when audio is present and "status on" when it is not. In this case the voltage indicates the alarm condition.
Recalibrate the channel if the RFC-1 reads a numeric value instead of a status on/off reading. If that does not work, check the channel programming. Help with telemetry channel programming is available on this page.
Setting up an alarm for loss of audio
This section provides the data for programming a telemetry alarm to monitor a channel with the AFS-3 connected. It does not cover the details of the programming operation. Help with alarm programming is available on this page.
If the AFS-3 is set so that RFC-1 reports "status on" when audio is present, program your alarm with an upper limit of "9999" and a lower limit of "0500". Use trigger rule 5 and trigger action sequence 1 to make telephone calls when an alarm occurs.
If the AFS-3 is set so that RFC-1 reports "status off" when audio is present, program your alarm with an upper limit of "1500" and a lower limit of "0000". Use trigger rule 5 and trigger action sequence 1 to make telephone calls when an alarm occurs.
When shipped from the factory, action sequence 1 is programmed to make the RFC-1 call the available telephone numbers. If that programming has been changed then use a different action sequence and adjust the alarm programming accordingly or the audio alarm may have undesirable results!
