I am calling the Read dialplan application from agi exec and I had multiple times that when the user did nothing it returned the letter A. This happened multiple times but only for the same caller and not for others. What does it mean?
I don’t have the asterisk verbose logs for that time.
DTMF digits are audio, which are recognized by a DSP implementation. Some voices (specifically female voices if I recall) can trigger it. ‘A’ is also valid DTMF.
The DTMF system uses a set of eight audio frequencies transmitted in pairs to represent 16 signals, represented by the ten digits, the letters A to D, and the symbols # and *. As the signals are audible tones in the voice frequency range, they can be transmitted through electrical repeaters and amplifiers, and over radio and microwave links, thus eliminating the need for intermediate operators on long-distance circuits.
Then you will need to handle this yourself. Read 1 digit at a time, and if it is A-D, loop again.
A through D are legitimate DTMF digits, no different than any other (I use them a fair amount myself). Systems that don’t account for them are poorly designed.
No. Talk off happens because DTMF is in-band at some stage. If it is in-band on the final hop, there will be no DTMF to detect. If it is out of band on the final hop, the talk off has already happened in converting to out of band.
But if if it in-band all the way, the muting will prevent Asterisk from detecting any digit I think the OP was hoping that you could prevent talk off by muting the audio, but still detect digits 0-9.
If it is VoIP all the way, the DTMF could never mix with the speech. Actually it wouldn’t really be DTMF. in that case, so the tones would never exist. DTMF was invented for in-band signalling on analogue connections.