[asterisk-biz] Any Cellular Phone Related Businesses in CanadaInterested in Call Transfers?

[Trixter aka Bret McDanel]

On Fri, 2008-08-01 at 13:42 -0400, Steve Totaro wrote:
> On Fri, Aug 1, 2008 at 1:30 PM, emist <emistz at gmail.com> wrote:
> > Hey Trixter,
> >
> > Can you explain a bit more about the "early media" adverts and why there
> > aren't any per minute charges?
> >
> > Thanks,
> >
> > Igor H.
> >
> 
> Try the first or second hits on Google.
> http://www.jdrosen.net/sip_early.html
> http://www.faqs.org/rfcs/rfc3960.html
> 
> You can send audio before answering, thus not be billed since the call
> was never answered.
> 

correct.  This enables you to open a media path, send audio (sometimes
receive it) and all that.  Its how "custom ring tones" are done, and
similar things.  I have noticed a bit of an issue relating to
international calls at least.  I set up a geographic number I had in no
media mode, meteor (Irish mobile company) routed a call there, and I was
able to hear perfectly fine, one way audio, no dtmf, and it cut me off
at exactly 60 seconds.

This is also how some error messages are sent (not all).  Really you can
send almost anything you wanted in this window, even conveying
information to the remote endpoint automagically (example would be a IP
route around to avoid pstn charges - a protocol exists that I wrote a
couple years ago but never did anything further with it, I heard that
some others were trying to do a modified version of what I did about a
year ago).  I should still have the pdf that I did of this protocol
(based on DTMF to make it more portable) if not I know that the people
who are doing a modified version have it because I gave it to them.

The reason you can open the audio path is because on the pstn the entire
circuit is allocated before the remote phone rings.  Since the circuit
is allocated, it is not that difficult to use it, answering supervision
(the signal that says the phone is now answered) is separate from
engaging the circuit.


-- 
Trixter http://www.0xdecafbad.com     Bret McDanel
Belfast +44 28 9099 6461        US +1 516 687 5200
http://www.trxtel.com the phone company that pays you!