[Asterisk-Users] call to a particular 800 number never shows answered on Zap channel

[Stewart Nelson]

> Whenever we call IBM, the call counter on the phone never starts and in
> the CLI the zap channel never gets the answered signal from the PRI.

First, there is nothing "unfair" or "illegal" going on.  Large toll-free
users have enough clout that they can negotiate contracts, where they
are not billed during the service selection phase of a call.  For example,
when you call American Airlines, billing doesn't start until an agent
answers, or the caller selects "automated flight information" or a similar
IVR service.  Answer supervision is used to tell the carrier when to start
billing.  This system is quite common and used by hundreds of companies.

With Asterisk, three things might go wrong:

You may hear ringing instead of the initial IVR greeting.  If your carrier
is sending 180 Ringing instead of 183 Progress (SIP) or Alerting without
inband audio (PRI), then they must fix the problem; nothing can be done at
your end.

You may hear the IVR answer, but can't control it, because your outbound
DTMF or voice is blocked.  Your carrier might be doing the blocking, in
which case they obviously must fix it.  However, there are also some SIP
phones and ATAs that don't send outgoing audio during Progress.  If you
have such, adjust the configuration if possible.  If not, you will need
to disable reinvites.

You may have two-way communication with the IVR, but the call gets
disconnected before answer supervision is received.   Find out if it's
your carrier or Asterisk that is timing out.  If the latter, just put
a longer timeout in your Dial statement; 180 seconds should be enough.

--Stewart