[Asterisk-Users] How to generate "ringing tone" to a calling party.

[Peter Svensson]

On Thu, 18 Nov 2004, Daniel wrote:

> >On Thu, 2004-11-18 at 12:05, Chad Scott wrote:
> >You *can* play a welcome message without >answering the line, however,
> >this doesn't always work. eg, I tried this >config on my PRI in Australia
> >(Telstra) and:
> >
> >a) Calling from a standard analog line I got my >welcome message as
> >expected
> >b) Calling from a mobile (Optus), I heard >silence until the call was
> >answered.
> 
> From the point of view of Telcos, situation "a" is not "as expected". If
> this occurs you could transmit a message without paying for the call. Of
> course it will be one-way but it will be useful. Imagine, you should set a
> short message (for about 1 minute) informing everything you want!

And that is exactly how the audio on isdn works in many places. The 
reverse audio path (from the called user to the caller) is opened as soon 
as possible. The caller is thus able to supply in band audio call progress 
information in addition to the isdn signalling. This allows e.g. custom 
ringing tones ("Paging Peter, Paging Peter"), custom busy messages etc 
without charging the caller.

The best place to generate ringing signals is at the last hop before the 
actual called phone. All earlier stages should cut through the audio from 
the last hop. 

This means that if asterisk calls an extension line (analog card, sip 
phone etc) it should generate ringing while if it calls another pbx (via 
eg. a pri) it should not. And guess what? Asterisk already supports all 
this! Use the 'r' option to the dial command where appropriate.

Peter