These adapters enable you to connect your Headset or Earphone with a 4-conductor 3.5mm Male Plug to the 2.5mm audio jack built into Cordless Telephones and Desktop Telephones.
There is one adapter that is made to work with Headsets and Earphones that were originally used with the OTMP / Samsung 4-conductor plug standard. Those earphones have a microphone built in, and they were made to function with Android phones that used the older OTMP wiring standard. If you have an earphone that was made to work with the original Samsung compatible OTMP cell phones, then you would want to order the SH2P telephone adapter.
We also have adapters made to work with earphones that were Apple compatible, and originally were made to work with the iPhone, Apple Laptops, the Apple iPad and Apple iPod. Those earphones have a built-in microphone and the plug is a 4-conductor TRRS male 3.5mm plug that is wired according to the CTIA / AHJ standard. Most all Apple compatible earphones will function with the AH2P telephone adapter, so you can communicate on your telephone using your Apple compatible earphone.