[Asterisk-Dev] PRI receive and answer supervision

Peter Svensson psvasterisk at psv.nu
Sun Jun 12 13:10:10 MST 2005

On Sun, 12 Jun 2005, Paul Cadach wrote:

> Matthew Simpson wrote:
> > > If you are getting early-media it is possible to detect that 'beep'
> > > without any Answer Supervision.
> > >
> > 
> > so telco PRI can have early media too  ? I thought that was a SIP only 
> > thing.  I'll have to have the lucent guys look at our switch then.. I think 
> > that is the problem. 
> Telco (always) provide early media when audio bearer service/progress
> indicators is negotiated. At least for EuroISDN.

An interesting detail is that the EuroISDN spec (EN 300 403-1) states in
annex K.2 that "Networks which choose to implement these procedures shall
ensure that they are not used on incoming international calls."

This refers to actually opening the reverse audio path from the 
B-subscriber to the A-subscriber. 


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