3.5mm headset adapter

I have a Sennheiser PC-21 II headset which I'm accustomed to using. I like it because the sound quality is good, it is worn over the head, only covers one ear, and it has a flexible boom microphone. My only complaint about it is that the cord is quite thin, not coiled, and extremely long. This is a picture of the box and if you look carefully you can see it describes the two analog 3.5mm connectors use to connect the headset to the computer.

Like the discussion in https://discussions.apple.com/thread/3895549 I'm writing here about a headset (speakers and microphone) and not headphones (speakers only). This is analog headset (not a USB) with two 3.5mm stereo jacks. One 3.5mm plug connects the speaker to the computer audio output, and a separate 3.5mm plug connects the boom microphone to the computer audio input.

Stereo plugs have three conductive areas commonly called TRS (Tip-Ring-Sleeve) as shown here: http://pinoutsguide.com/Home/Tele35s_pinout.shtml

Apple devices use a plug with four conductive areas commonly called TRRS (Tip-Ring-Ring-Sleeve) shown in this description: http://pinouts.ru/HeadsetsHeadphones/iphone_headphone_pinout.shtml

From these descriptions it is straightforward to adapt an Apple TRRS connector to split out a stereo speaker connector, and mono-microphone connector.

Unfortunately there is no universal standard for these kinds of things. Another obvious configuration is to switch the roles of the Sleeve and it's closest Ring as shown in this description: http://pinoutsguide.com/HeadsetsHeadphones/nokia_N78_headset_pinout.shtml

This means that there is no such thing as a universal adapter. When you purchase an adapter you have to pay attention to its wiring configuration (usually impossible because manufacturers address a largely non-technical audience), or look closely at what devices it claims to be compatible with.

After searching through many sites and discussion threads, I found the StarTech MUYHSMFF adapter as a solution that seems to be currently relatively easy to obtain: http://www.startech.com/Cables/Audio-Video/Audio-Cables/35mm-4-Position-to-2x-3- Position-35mm-Headset-Splitter-Adapter-Male-to-Female~MUYHSMFF

Most sites carry a rather poor image of this adapter, but, as shown below, there are some good pictures are available that show the two 3.5mm stereo sockets are embossed to show which accepts the microphone and which accepts the speaker.

There is one final problem. The electrical characteristics of the microphone (or speaker) might not be acceptable to the computer audio circuitry. You might want to plug each into the audio socket individually to verify that they are electrically compatible before buying an adapter to combine their operation.