[Asterisk-Users] How to avoid collect calls on ISDN BRI trunks?

[Dhennys Pestana]

Hello, friends.

I need to block collect calls on my PBX.

I was able to find information on Google regarding ISDN ZAP channels, but not
ISDN CAPI channels which is my case.

Since there's no information from the Telco that the call is going to be charged
by the callee, if a particular call is automatically answered by the PBX instead
of a real person there's no way to avoid it. There's only a recording AFTER the
call is answered, asking for the callee party to accept it.

By using ZAP channels with HFC ISDN cards, it's possible to use Hangup() and
Flash() commands, which won't do any good on CAPI channels because it will
hangup the call immediatelly.

Note: This situation is exctaly the same with remote access servers (RAS),
commonly used by Internet Service Providers.

Here's an example of what should happen on my scenario:

[default]                         ; External calls comes on "default" context
exten => s,1,Wait,1               ; Wait for all ISDN and CAPI messages
exten => s,2,Answer()             ; PBX actually answers the call
exten => s,3,Wait,1               ; Just in case
exten => s,4,Flash()              ; Avoid collect calls, don't actually hangup
exten => s,5,Wait,1               ; Wait a second (just in case)
exten => s,6,Answer()             ; Now it should work as if it were "s,1"
exten => s,7,BackGround(IVR-menu) ; 1 for sales, 2 for support, 3 for...


Note: Step "s,4" could be also "Hangup()", it won't make any difference.

If it were an analog trunk, it would work flawlessly. Unfortunatelly for digital
trunks, when you hangup the channel the call is dropped immediately.

I'm pretty sure it's not an Asterisk issue, but it's definitely related.

Thanks in advance for any input on this matter.


Regards,

-Dhennys