external microphone jack not working on Satellite C55-B5115KM

Hello,

I have a Toshiba Satellite C55-B5115KM and a Linux Devuan system.
I've been trying to make the external microphone work, using both a TRS jack and a TRRS adapter.
The jack on the laptop works fine when i use headphones (muting the speakers and playing sound through the headphones) but when i use the same jack for an external microphone bot with TRS or TRRS 3.5 jack, the speakers are muted but built-in microphone continues to work.

According to the user manual this jack is:
A 3.5 mm mini headphone/microphone combo jack enables connection of a monaural microphone or a stereo headphone.
It seem strange that the jack is malfunctioning because this behavior never changes and the headphones works fine.

Any suggestions as to how troubleshoot the issue?

 

Check out external microphone connector's standard, CTIA or OMTP?
Or try with a CTIA-OMTP Audio adapter.

 

Thanks for the suggestion. Do you have any idea which standard the laptop jack is? I couldn't find this specific information anywhere.