No sound on outgoing calls

[Ryta]

We are using phones yealink that work well but Т-20 и Т-20 Р have problem:
outgoing call - on the other party they can not hear the caller. The caller hears their but they not hear him.
What can be the causing this?
Thanks.

[Karl_Yealink]

Do you mean that only the T20P call to T20P, there is no sound on outgoing call?
And if you use the T20P call to other phones, it can work normally?

Please tell me the firmware of the phones?
And how many phones do you have? All of them have this problem?

[Ryta]

- If I use the T20P call to T20P and the T20P call to other phones there is no sound on outgoing call.
- The firmware of the phones is 9.73.0.50
- I have two phones T20P and both the phones have this problem.
- Phones of other models have no this problem.

[Karl_Yealink]

Please tell me the firmware of other models which don't have this problem.
And please help us to get the PCAP files, we can check something from them.
You can know how to do from the FAQ: http://support.yealink.com/faq/faqInfo?id=311