Hi Sir，
About your issue, in order to make your scenario more clear, let us check if the information are right below:
1. When there is an external incoming call, the employee can hear the call ring, but when they answer the call, they can’t hear any audio, right?
2. The internal incoming call work normally?
3. T21P E2 and VP530 have the issue, but T20P can work normally?
4. You listen to the record of the call, and find both voice of the two side are recorded, right? Can you kindly tell me how can you get the record?
In order to do more trouble shooting, please share us more information below:
1. Can you kindly provide the level 6 syslog, config.bin and pace trace of T21P E2 and VP530 for us when you reproduce the issue.
About how to get the three files, please refer to the link below:
http://support.yealink.com/faq/faqInfo?id=313
2. To make a comparison, please provide the level 6 syslog, config.bin and pace trace of the T20P.
3. When you get the pace trace, please also capture the pace trace in the PBX, since we can see the behavior of the server from it.
4. Is the issue happened every time when receive the external incoming call? If not? How often it will happen? Such as twice a day?
It would be better if you can provide the three files of the T21P E2 and VP530 when they can receive an external incoming call normally to make a comparison.
Please note to update the firmware of both phone to the latest firmware then do the test. You can download the latest firmware in Yealink website:
http://support.yealink.com/documentFront...isplayPage
5. How many phones you have in total? And how many of them have the issue?
Thank you for your information in advanced.
Best Regards,
Lucia Lu
