Technical Support
Connecting the AFS-3 to the RFC-1/B
While originally designed to be a standalone device, the AFS-3 Audio Failsafe is most commonly used with the RFC-1/B. The output relay of the AFS-3 is connected to a telemetry input of the RFC-1/B. The relay switches a voltage and the RFC-1/B senses loss of audio based on the voltage.
This procedure involves only low voltage circuits. High voltages are present in the transmitter environment and may be in the vicinity of the RFC-1/B. High voltage circuits are capable of delivering a lethal shock! If you are not comfortable in the environment please do not continue with this procedure.
Enabling the AFS-3 signal voltage
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 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 JP4 to engage +5 VDC on the relay common pole.
- Install a jumper at JP2 to have +5 VDC present when audio is present, or
- Install a jumper at JP3 to have +5 VDC present when audio fails
Install JP4 and then install either JP2 or JP3. Remember which jumper you installed, JP2 or JP3. This will be important for setting up the alarm. Re-assemble the AFS-3 by sliding the PCB back into the chassis rails. Attach the rear panel its two screws.
Connecting the AFS-3 status signal
A pair of wires connect the AFS-3 output to a telemetry input on the relay panel of the RFC-1/B system. This connection carries the +5 VDC status signal.
- Connect the AFS-3 relay COM terminal to the "+" telemetry input
- If JP2 was used, connect the AFS-3 relay NO terminal to the "-" telemetry input
- If JP3 was used, 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/B may require calibration. Connect to the RFC-1/B and select the channel to which the AFS-3 has been connected.
If JP2 was installed, the RFC-1/B 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, the RFC-1/B should report "status off" when audio is present and "status on" when it is not. In this case the voltage indicates the alarm condition.
Adjust the calibration pot if the RFC-1/B reads a numeric value instead of a status on/off reading. The channel programming affects the reading. See the Links section of this page for programming assistance.
Setting an alarm for loss of audio
The RFC-1/B reports the AFS-3 status signal as a simple status on/off reading. The RFC-1/B alarm system requires numbers for the upper and lower limits. Background information on how this works appears elsewhere on this site and in the RFC-1/B documentation. For this discussion we present two simple rules.
- If the AFS-3 is set so that RFC-1/B reports "status on" when audio is present, program your alarm with an upper limit of "9999" and a lower limit of "0500".
- If the AFS-3 is set so that RFC-1/B reports "status off" when audio is present, program your alarm with an upper limit of "1500" and a lower limit of "0000".
You will, of course, have to supply the correct channel number when programming the alarm. Assuming that the default settings for the other alarm parameters are used, the RFC-1/B will call with a telemetry alarm when the audio fails.
See the Links section of this page for more alarm programming assistance.