[asterisk-users] Detecting answer with an analogue card

[shadowym]

I have not had any problems with hangup detection in N America. At least not
with Sangoma cards in Eastern and Western Canada.  As long as the central
office your analog lines are connected to support kewlstart which means they
momentarily disconnect the loop current when the other end hangs up.  I
think almost all if not all central offices support this now a days.

That's the easy part.  The problem I have run into is answer detection.  A
lot of central offices do not support this.  If they do usually it is done
by reversing the polarity.  If lines don't have this then you have to set
Asterisk to automatically just assumes the line is answered after it dials
which is a problem for some things like forwarding to a landline phone or
cell but still wanting to switch to voicemail if nobody answers after x
seconds.

The call progress detection in Asterisk that tries to listen to the sound to
try figure out what is happening is not usable at all.  Way too many false
detections. 

-----Original Message-----
From: Stephen Bosch [mailto:posting at vodacomm.ca] 
Sent: Monday, February 05, 2007 11:59 AM
To: Asterisk Users Mailing List - Non-Commercial Discussion
Subject: Re: [asterisk-users] Detecting answer with an analogue card

Andrew Kohlsmith wrote:
> On Monday 05 February 2007 8:26 am, Stefano Corsi wrote:
>> Uhm... I still don't understand... Does call progress detection work 
>> fairly well for analog cards with the US telephony system, or it's 
>> still something experimental and randomly working? And if it's 
>> working in US, how difficult can it be to port it to the (for
>> example) Italian system?
> 
> Put it this way: Any serious Asterisk install that wants to pass the 
> wife test will have "progressinband" turned off in a fairly short order.

For those of us without first-hand experience here, what happens when using
"progressinband"?

My own experience is that call progress detection -- mostly with respect to
remote hangup detection -- is spotty, and I'm in North America.

>> As an alternative, what about having a device (let's say Inalp Patton
>> gateways) connecting to the telco with ISDN and to Asterisk with 
>> ethernet/SIP. Should I get correct ANSWER detection (and thus correct 
>> billing CDR records) with this setup?
> 
> I think you're starting to reach beyond what's practical.  But yes, 
> something like that would work just fine, because both ISDN BRI/PRI 
> and SIP are digital protocols and employ the concept of line state 
> beyond the simple "on hook/offhook".

..and at this point, why wouldn't you just put a BRI card in the Asterisk
server and skip the intermediate hardware?

-Stephen-