[OpenSER-Users] Cellphones and voicemail

Christian Schlatter cs at unc.edu
Tue Nov 6 03:50:32 CET 2007


Chris Heiser wrote:
> Trying to send a user's call to their cellphone can be problematic, 
> especially when their phone is off, bad signal, etc...  I know some 
> carriers send q931 messages back when a call is redirected (sometimes), 
> but not all do.

Well, most of them don't because they normally make money with every 
voicemail call. At least here in the US it is also very difficult to 
turn off the cell voicemail, that normally includes a call to the 
carrier's helpdesk.

> 
> Is it possible to make a determination in OpenSER (if we know we're 
> sending to a cell phone) that the call was picked up too quickly?  That's 
> really the ugly problem.  If I could say, "Oh yeah, you're cellphone 
> picked up in less than 1 second, a real person probably didn't do that." 
> and drop that fork, that would be awesome.

There is unfortunately no good solution for this problem. Asterisk has a 
'Answering Machine Detection' module 
(http://svn.digium.com/view/asterisk/branches/1.4/configs/amd.conf.sample?view=markup) 
that implements some heuristics for voicemail detection. In my opinion 
this will never work perfect and you'll end up with false positives.

/Christian

> --Chris
> 
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