[Asterisk-Dev] Answer Supervision for incoming calls in Asterisk

[Adam Goryachev]

On Sun, 2005-03-20 at 23:09 -0700, Kevin P. Fleming wrote:
> Adam Goryachev wrote:
> 
> > However, when calling from my mobile phone (Optus Australia) to
> > asterisk, and doing this, I didn't hear anything from the playback, just
> > silence. Eventually, asterisk answers, and then I hear audio. (Even
> > though it worked from landlines, and other mobiles). So, your 'warning'
> > may not be enough for some people ??
> 
> That's correct; not every path through the PSTN allows for early audio 
> delivery. Mobile phones frequently do not, and also frequently do not 
> allow access to premium numbers anyway :-)

Is there some known work-around for this? Even if we could 'detect'
this, and then answer the call before playing the welcome message?
Somehow, I don't think that's possible though, which means either some
people hear a lengthy silence, while others will hear things as normal.

Surely there is a better method?

PS, what if you wanted to use this feature for a 1800 number, to reduce
your (the receivers) cost? Or for a normal number where most of your
callers are long distance, and hence you want to reduce the callers cost
while waiting for a real person to answer.... ie, doesn't need to be a
premium rate number, there are plenty of other places it might be used.

PPS, how about setting up two systems in 'long distance/country' away,
and using two lines to call between them. Conference in the two lines
(without answering either of them) and you can have a normal
conversation....

Caller -> PSTN A -> *a <= 2xPSTN Lines => *b -> PSTN B -> Dest

PSTN A and PSTN B are 'answered' and act like normal calls. *a calls *b,
which doesn't answer, and automatically creates a second call back to *a
on another PSTN line. *a doesn't answer the call, but adds it to a
conference with PSTN A, and the first call it placed to *b and the call
just received from *b.

*b places a call to Dest, which is answered when the recipient picks up
the phone. It places the Dest call into a conference along with the call
it received from *a (but didn't answer) and the call *b placed to *a.

Thus, each of the 2xPSTN lines are one-way, but in different directions.
Overall effect, is free phone call.... Sure, it is really messy, and
maybe it wouldn't work in all circumstances, but it was just a
thought :)

Regards,
Adam