Fast DTMF on Denton city system

[KVL3000]

Heard this on the Denton City trunked system. Whats strange is, My scanner didn't hear the DTMF, and im only scanning the UNT talkgroups which do not have any data
Video

 

[IAmSixNine]

Reminds me of the old ANI stuff used for radio identification.
I never heard it on trunked systems. Just conventional analog channels about 15 or 20 years ago.
Anybody else think thats what it sounds like.

 

[Motoballa]

Yeah when he sent me the snapchat of it I was like whaaaaaat lol. I will say years ago when I was in Lewisville during a storm I listening to their siren activation frequency (VHF conventional), I first heard a set of DTMF tones then data packets like MDC and it repeated 3 times then the sirens went on.

Obviously in this case I don't think it's for that but perhaps its a heartbeat being sent every x seconds to a monitor somewhere? Not sure.

 

[Project25_MASTR]

On analog trunking you can run MDC, ANI or even two-tone on top of a regular voice channel if using encoders/decoders which are directly interfaced to the audio circuitry of the SM. As long as the high pass filter used for sub-audible data doesn't cut it, you are good to go. When you think about it in terms of conversion, it makes sense. Conventional to analog trunking, just swap the radios out and reuse the old encoder/decoders. Analog to digital takes a bit more effort and money (which is why analog signalling is still used to compliment digital all over the state).

 

[KVL3000]

Whats strange about all of this, normally I only hear this on siren test days as each siren is activated. I took that video on a tuesday, and denton tests on wednesday at noon. Otherwise, I never hear this at all, I only heard it on the XTS, but not the APX

 

[nd5y]

Whats strange about all of this, normally I only hear this on siren test days as each siren is activated. I took that video on a tuesday, and denton tests on wednesday at noon. Otherwise, I never hear this at all, I only heard it on the XTS, but not the APX

It still could be sirens. Some systems do periodic (daily, weekly, etc.) status polling.

 

[IAmSixNine]

To add to this, i thought i hear the same thing a few days ago when The Colony FD was dispatching a fire call.

 

[Russell]

If you hear it on-scene ... it was an analog way to unlock the knox-box key on an engine.

 

[nd5y]

I have seen several FDs that send a 4 DTMF tone sequence right before the QC tones for each station.

 

[Project25_MASTR]

If you hear it on-scene ... it was an analog way to unlock the knox-box key on an engine.

In Austin they are doing this with the page function in P25 for gated communities.