[Asterisk-Users] DTMF tones not long enough on out going call s

[Adam Roach]

Low, Adam [mailto:ALow at Prioritytelecom.com] writes:
...
> What is the reason for this? Is the PBX actually cancelling 
> out the DTMF tone after it itself recognises the tone? 

No; the phone is sending the information symbolically instead
of encoding it using a traditional codec. It's up to the recipient
(Asterisk in this case) to interpret them correctly.

> Does 
> it also effect the DTMF tones received over a B channel from the PSTN?

Not over a B channel, since those *are* in-band. They're encoded
just like voice is. On the other hand, Q.931 specifies a D-channel
encoding of keypresses as well. I'm not familiar enough with
actual ISDN terminal implementations to know whether they tend to
send in-band, out-of-band, or both. I would guess that behavior at
Asterisk would depend heavily on this factor.

(Note that I don't consider myself an ISDN expert, and my knowledge
in this area is only what I can recall after four years.)

/a