3 ms·
It's probably something on the VHF frequency which you can pick up via a cheap $15-20 RTL-SDR. If it was installed that long ago there's a good chance it runs o
by vvanders 8y ago
It's probably something on the VHF frequency which you can pick up via a cheap $15-20 RTL-SDR. If it was installed that long ago there's a good chance it runs on something really simple like DTMF tones.
Something like the 433Mhz ISM band parsing can give you an idea of what's possible[1].
[1] https://www.rtl-sdr.com/tag/rtl_433/ https://www.rtl-sdr.com/tag/rtl_433/