[asterisk-dev] ISDN gurus - getting isdn call progress ??

[Matthew Fredrickson]

On Nov 15, 2006, at 3:32 AM, Kai Militzer wrote:

> Hi,
>
> On 15.11.2006 01:36, Steve Kennedy wrote:
>> On Tue, Nov 14, 2006 at 04:35:49PM -0600, Kevin P. Fleming wrote:
>>> Julian Lyndon-Smith wrote:
>>>> we have an ISDN-30 Euro connection. When dialling out is it 
>>>> possible to
>>>> stop a call when it is about to start ringing ? (i.e is there an 
>>>> ISDN
>>>> message that says "yup, this is a valid number, starting to ring 
>>>> now" ?)
>>> The message tells you that the call has _begun_ ringing, not that the
>>> call is being placed. I don't know of any signaling that you could 
>>> use
>>> just to verify that numbers are dialable, without actually placing 
>>> the
>>> calls and then dropping them.
>
>> You should be able to do that at the ISDN signalling layer, or via 
>> SS7.

IIRC, ACM maps directly to ISDN Proceeding, so that might be a way to 
do it.  If you receive a proceeding message, you could consider it 
valid.  Though I'm not absolutely sure that that would be a qualifier 
for a valid number.

Matthew Fredrickson