Solved No audio when transfering external call to external number

[Eric Jan]

When I try to forward a call with an outside number to another external number, both ends hear nothing.

If I set up forwarding to an external number directly on a DID, it works when I call the DID from outside.

If I set up forwarding on the extension, and try to transfer an external call to the extension -> no sound as well for both ends. If however I transfer an internal call to the extension, the forwarding works.

Could this be a firewall problem? The firewall check completes successfully.
Or might it be a problem with our VoIP Provider (SipCall)?

 

[eddv123]

Can you define what you mean here - I am translating - forward an outside call (caller not on your 3CX PBX) being forwarded to another outside number (not on your 3CX PBX).

In this case the call would no longer be on your PBX and thus should not be your issue - please advise if I have mis-understood anything.

 

[craigreilly]

Why would the call not be on the PBX anymore?
The call came in on 3cx... someone answered it then forwards it to an external number.
3cx holds onto this call.

 

[Eric Jan]

Can you define what you mean here - I am translating - forward an outside call (caller not on your 3CX PBX) being forwarded to another outside number (not on your 3CX PBX).

In this case the call would no longer be on your PBX and thus should not be your issue - please advise if I have mis-understood anything.

No, you understood this corectly. Lets thake this scenario:
A customer calls us and needs to talk with Mr. X. Mr. X is however out of office, so I try to forward the call to his mobile phone. As expected (doesn't matter if attended transfer or blind transfer) my calls with both people (customer and Mr. X) end, as soon as the procedure is completed. In the PBX i can still see the active call between those two people, however they both don't hear anything.

If however I define a forwarding-rule on Mr. X's DID directly to his mobile phone, and the customer calls this DID, the call is also visible in the PBX but they have normal sound.

 

[eddv123]

Interesting.... If a call is passed between extensions within 3CX I would expect this behavior but not when transferred to an external number on another network or system.

Either way, have you tried "PBX delivers audio" on/off ? it can be found in the Extension settings under Options.

 

[Eric Jan]

Interesting.... If a call is passed between extensions within 3CX I would expect this behavior but not when transferred to an external number on another network or system.

Either way, have you tried "PBX delivers audio" on/off ? it can be found in the Extension settings under Options.

That seems to have worked. I had to enable "PBX delivers audio" on the SIP-Trunk and on the extensions, and disable "Support Re-Invites" and "Support 'Replaces' header".

Thank you for your help

 

[eddv123]

Great! happy to have helped.

 

[Eric Jan]

Just a short update. I had to re-enable "Support Re-Invites" and "Support 'Replaces' header" on the extensions, because otherwise calls coming to a call-queue had no audio.

So currently I have on the SIP Trunk:
PBX Delivers Audio: disabled
Supports Re-Invite: disabled
Support Replaces: disabled

and on the extensions:
PBX Delivers Audio: enabled
Supports Re-Invite: enabled
Support Replaces: enabled

Everything seems to be working, so let's hope it stays that way.

 

[YiannisH_3CX]

Hello @Eric Jan

Glad to see the issue has been resolved. The only change you should make in your config is to enable the PBX delivers audio option on the SIP trunk.