Recently I was having a problem with both my laptop and Surface Dock 2 registering my external desktop microphone and Zoom F1 recorder as headphones. It was frustrating, because the technical specifications specify that the 3.5 audio jack on both devices can be used with a microphone. I had checked the sound settings and device drivers, and everything seemed to be working fine.
I had completely overlooked the fact that the audio ports were type TRRS*, while the cable jacks were type TRS, and that both the laptop and the dock by default expect headphones. Both my recorder and desktop microphone are capable of stereo recording. My thinking was that they will be recognized as multichannel input source and Windows will handle the difference between the two types. I was disappointed.
To get this situation resolved I ended up buying a TRS to TRRS port-to-jack adapter. While there is single port to jack adapters, I chose to buy a split one. Since, multichannel input is not an option, I might as well use the headphones output support of the audio port. Now I can plug in both my microphone and headphones at the same time.
* TRRS – Tip-Ring-Ring-Sleeve. The type of contacts on the 3.5 mm jack. They can range from stereo output with microphone input (TRRS), to stereo (TRS), to mono (TS). Keep in mind that this type of jack has applications beyond audio, e.g. power delivery in some devices.