Tamper Alarm for remote TXers.
Posted: Thu Aug 31, 2006 11:05 pm
Mark,
Heres a simple suggestion for an optional module. It is a simple card with a set of N/O and N/C contacts which detect an alarm condition (Such as the TX being lifted or opened... or, perhaps, the rooftop access door being opened)
Upon tripping the alarm...
either:
- An audible alarm signal is injected/replaced into the audio for a second or two
- The RDS broadcasts the alarm on an unused code (Or, you could re-use the traffic switch)
Meanwhile...
Back in the studio a second module responds to either the RDS or the audio tone (PLL, DTMF Decoder or an off-the-shelf RDS decoder IC) and switches a load. The load could be an LED... a buzzer... anything to alert the operator that the Transmitter has been located/tampered and that the channel may soon go down.
The audio version is simple and cheap... it would simply insert into the audio chain. At the studio a standard radio receiver is interfaced to the audio detect circuitry via the headphone jack.
The RDS version would be suitable for those already using an RDS encoder... it could connect to the traffic-announce switch or, given a slight firmware modification, to a dedicated 'alarm' input.
Cost is minimal.
-Medus
Heres a simple suggestion for an optional module. It is a simple card with a set of N/O and N/C contacts which detect an alarm condition (Such as the TX being lifted or opened... or, perhaps, the rooftop access door being opened)
Upon tripping the alarm...
either:
- An audible alarm signal is injected/replaced into the audio for a second or two
- The RDS broadcasts the alarm on an unused code (Or, you could re-use the traffic switch)
Meanwhile...
Back in the studio a second module responds to either the RDS or the audio tone (PLL, DTMF Decoder or an off-the-shelf RDS decoder IC) and switches a load. The load could be an LED... a buzzer... anything to alert the operator that the Transmitter has been located/tampered and that the channel may soon go down.
The audio version is simple and cheap... it would simply insert into the audio chain. At the studio a standard radio receiver is interfaced to the audio detect circuitry via the headphone jack.
The RDS version would be suitable for those already using an RDS encoder... it could connect to the traffic-announce switch or, given a slight firmware modification, to a dedicated 'alarm' input.
Cost is minimal.
-Medus