"Dial sound" with Whelen voice

[MattDean1003]

I found a video on youtube of Gatlinburg, TN's sirens being tested. I've seen these sirens plenty of times, and I've taken pictures of the siren tested in this video, but I also noticed that there is a dial tone sound that is featured in some more of our Whelen videos. This looks to be one of the newer Whelen types, like the Vortex without the wind vane. The folks I talked to the last time we were up there said the sirens were put up in the early 90's, however. Plus, it does do voice, as you can see.

Point of this topic. Why is there a "dial tone sound" that chimes like that right after the voice? Here is the link.

http://youtube.com/watch?v=7qE72MxXS-U& ... ed&search=

[AllSafe]

DTMF (dual-tone multi-frequency) tones transmitted with the voice signal. They are used to control the siren. It is usually a sequence of numbers with * and # to mark the beginning and end of the tone sequence.

[JasonC]

Yup. Thats's just the DTMF controller sending a signal such as "rotate right 90 degrees" or "report status", etc. Whether or not this can be disabled from rebroadcasting ove the speaker, probably, but I dont know for sure as I don't own a Whelen.

[Robert Gift]

I find no problem with the DTMF broadcasting, but I doubt it is supposed to come through over the speakers.

[Justin]

I find no problem with the DTMF broadcasting, but I doubt it is supposed to come through over the speakers.

Same. I remember the videos with someone (AllAmericanFE?) walking around with his camera filming the sirens do the dial tone.

Bug in the firmware/system software? That said, could be a 'feature' to indicate that the siren is working, rather than just acting weird; albeit a confusing one...

[jkvernon]

With live voice it is suposed to do that. It doesn't indicate anything, it just does it. Here's basically how it works. A DTMF signal is sent to the sirens which tells them to turn on and broadcast whatever is being sent into the mic from the activation point, kinda like a bunch of baby monitors. Whatever signal is sent to the siren, whether it's DTMF or an announcement is then broadcasted through the speakersuntil the signal for the speakers to turn off is sent out.

[Robert Gift]

I would expect not to hear the first DTMF because it would then turn on the siren.
I can understand hearing the second command which is to turn off or change system mode, etc.

[SirenEnthusiast360]

What sort of device do they use to transmit the dtmf tones? Do they have some sort of special telephone?

[jkvernon]

No, actually the activation control board plays whatever DTMF tones it's programmed to play. All Whelens basically use the same basic DTMF signal to control their sirens.

[SirenEnthusiast360]

I see, so your saying it wouldn't be possible to "dial a siren" to make it go off?