No audio on attended transfers

[HSGrocer]

Hello everyone.

We have a 3cx system with a small office of 16 users. Calls come in via a digital receptionist to different call groups. The issue we have is that when a call needs to be transferred to another extension within the office the audio drops out from the originating caller to the extension that the call is being made to. If you hang up and it becomes an attandended transfer the call is fine once it is answered again.

We are using Yealink T53W handsets.

Does anyone have any suggestions on what might be going wrong?

 

[eddv123]

Have had a similar issue with call pickup and no audio (still in progress however).

Try PBX delivers audio on the extensions in question, if it still fails run a PCAP trace from the PBX to capture all parties involved and see which is without an audio stream - most likely it is an issue with the network blocking the port somewhere.

 

[HSGrocer]

Thanks - will give that a go. I had "PABX Delivers Audio" enabled on the caller extension, but not the callee - Have made the change across the office to see if that helps

 

[Cytranic]

Make sure PBX Delivers audio is also checked in your sip trunk

 

[HSGrocer]

Thanks everyone - Checked both those options and it still seems to he happening - Only on attendended transfers from my extension.
Any other suggestions?

 

[cobaltit]

https://www.3cx.com/community/threads/information-to-provide-when-requesting-help.67558/

More information about your setup would help.

 

[eddv123]

from my extension.

The key question then would be what is different about your extension compared to everyone else, this would include.

• Location.
• Make and model of phone.
• Firmware version.
• Custom or standard template used.

 

[HSGrocer]

Thanks everyone. The info requested is below

• 3CX Version, Pro Annual 16.0.9.10
• Is the 3CX Server Hosted and where? Hosted in our datacenter by a third party
• IP Phone Make/Model/Firmware Yealink T53W
• Provisioning Method: Local / VPN / STUN / SBC Local
• Trunk Provider Bendigo Telco (AAPT)
• Has the Firewall Checker passed: YES
• Are custom Phone Templates being used: YES - Only to remove the logo flash
• Firmware 95.84.0.35

Another thing that might possibly be causing it - Im one of three people in the office who use the desk phone, the soft phone (Only to monitor the calls) and the IOS app - Could that be causing the issue?

 

[eddv123]

Another thing that might possibly be causing it - Im one of three people in the office who use the desk phone, the soft phone (Only to monitor the calls) and the IOS app - Could that be causing the issue?

I dont think so, SIP allows for multiple endpoints to be registered to a single extension at anyone time, it will fork the calls and whichever extension picks up will receive the audio.

The issue I had which was similar to this one was (as suspected a networking issue) it was passed over to the 3rd party IT company to deal with.

 

[JohnS_3CX]

Hi @HSGrocer

Can you replicate this behavior on demand or is it an occasional problem?

 

[HSGrocer]

Hi @HSGrocer

Can you replicate this behavior on demand or is it an occasional problem?

Used to be random - but now seems to be almost every transfer. Its only the transfer - the main audio on either a direct internal or external call works fine

 

[JohnS_3CX]

Ok if you can replicate it then I would suggest the following:

1. Reset two phones to factory
2. Reprovision them using the default 3CX templates
3. Ensure your trunk options don't have Supports Re-invite/Replaces

Now when one of those phones receives calls, and transfers to the other phone, see if the problem goes away. Repeat a few times and let them run like this to see if the issue goes away.

Ignore the issue with the rest of the extensions, until these two provide evidence of a solution.