One-way voice when transferring calls to external numbers

[Edward]

We're using the Free version of the 3CX PABX and we're very impressed with its features and ease of use. However, there's one thing we're struggling with...

We have a problem when transferring calls to an external number. The call transfers successfully to the external number (e.g. mobile cell phone) but the audio only works on-way. By that I mean, one end can hear the other but not the other way around.

Directly calling the external numbers from a 3CX extension works fine.

Example:
Ext 100 calls Ext 101 : Ext 100 and Ext 101 connected with 2-way voice
Ext 101 transfers call to external number 987654321: Ext 100 and 987654321 connected but only with 1-way voice

We've tried each of our lines and this problem happens if the call is transferred out to the external number via PSTN (LinkSys SPA 3102), Sipgate (SIP provider) or WebCallDirect (SIP provider).

By the way, transferring an incoming external call between internal extensions works fine.

Is this a limitation of the 3CX PABX or am I missing a setting somewhere ?

Thanks in advance for any help.

Edward

 

[landfiets]

It could be a codec problem. Look what codecs you use in your 3CX system.
Also it sounds like a possible port problem. What did the firewall test say?
My main thoughts go to the codec thing.

 

[Edward]

Hi landfiets - thanks for the reply

Firewall test:
This comes back with "Result: Firewall check passed!"
As I can make and receive calls via SIP providers, I assume that the firewall is ok.
I have not make any changes to my firewall - I am relying on the stun server (stun.3cx.com) to open the ports for me.
Please feel free to suggest any checks that I could do to make sure everything is ok.

Codecs:
I have had a look at the 3CX web-based Gateway Configuration and I can't find any reference to any codecs.
On the 3CX VoIP Client, codecs are listed in the following order:
PCMU
PCMA
GSM
I'm not sure what it is that I should do to to check that I have the right codecs installed/configured. Any advice would be much appreciated.

Thanks

Edward

 

[landfiets]

you can find the codecs for the lines in the manage voiplines.
there you can say what codecs you prefer and which not.
you have to check and test this with calling yourself by cellphone and try to transfer it.

Try this, by changing priority for the codecs.

 

[Edward]

Hi landfiets

Problem solved!

The problem was not caused by codecs - it was due to the 3CX VoIP Client I was using.

Running through the same tests using an hardware VoIP phone (LinkSys SPA941) and an ATA (LinkSys PAP2T) the problem went away. I only experience the problem when using the 3CX VoIP client.

Thanks for your help.