This TRRS 4 Conductor adapter simply switches the microphone and ground channels around. It is sometimes needed when you have a set of headphones with a built in microphone that is incompatible with your device because of the wiring standard it was created for.

Here is a detailed explanation of the two standards.

The CTIA (Cellular Telecommunications Industry Association) and OMTP (Open Mobile Terminal Platform) are two different organizations that have created standards for audio connectors used in mobile devices, specifically for the arrangement of the audio and microphone pins.

In terms of popularity and widespread adoption, the CTIA standard is more common. The majority of smartphones and mobile devices, particularly those manufactured in the United States and other parts of the Americas, follow the CTIA standard. In the CTIA standard, the audio jack has the following pin arrangement: left audio, right audio, ground, and microphone.

On the other hand, the OMTP standard is less commonly used. It was primarily adopted by older mobile devices, especially those manufactured in Europe and Asia. The OMTP standard has a different pin arrangement for the audio jack: left audio, right audio, microphone, and ground.