The COM Button can be programmed with different functions, like mute or push to talk.
To connect the command adapter to the SEK:
Connect the 3-pin audio connector of the COM button to the microphone / instrument input socket of the SEK.
Connect the 3-pin audio connector of the Sennheiser microphone or the Sennheiser CI 1 line/instrument cable to the 3-pin audio socket of the COM Button.