The offered item changes the poles of MIC and GND of occupancy. Therefore you can, for example, an Android-Headset (with single button for operation on micro) use on a Nokia phone. In my case, a Nokia C3-00.
It works the button remote control (eg accept call or "next song") and the microphone properly.
Unfortunately, many confuse the product with a pure "line-out" adapter. This would easily switch from 4- to 3-pole. Therefore, the bad reviews come.
