Problem Description : Fail to use earphone on IP phone
Analysis Progress :
1) Long press the “Home” button at the IP phone and “Restore” the settings
2) Reboot your IP phone
3) Understand the audio source feature. You may refer the photo below. 
Plantronics brand is recommended. This is the earphone that weusing to test based on your scenario.
4) Confirm the settings (Preferences > Audio Source > Headset (RJ-9) > Save )
5) Plug in your Earphone(RJ9) to the Headsetport.
Noted : By default, the earphonewill not have a sound when plugging in. You need to test call and see whetherthe earphone have sound or not.
6) Try to callsome endpoint and see whether the earphone can hear the voice from another endpoint or not.
Noted : If your earphone is not Plantronics brand it maycause you fail to hear the voice from another endpoint.
Root Cause : The brand of the earphone not support by / not compatible with IP phone
Solution Description : As tested in our lab, the IP phone can support Plantronics brand. Customer request to close first and will use Plantronics brand earphone to try. Will follow up with this issue with customer.
