Sennheiser SD series User Manual page 27

Making calls using the headset
26 | SD Series - User Guide
Managing calls using the "HeadSetup" call control functionality
Accepting a call: The softphone signals that you are receiving a call. You
hear a ring tone in the headset.
Press the Link button on the headset to accept the call.
Making a call:
Start the call using your softphone, the audio signal is automatically
transmitted to the headset.
Ending a call:
Press the Link button. If the other party hangs up, your softphone and
your headset become automatically ready to receive the next call.