You can mute the microphone so other parties can’t hear you. Microphone Mute applies to all modes (handset, headset, and speakerphone). You can still hear all other parties when you mute the microphone.
To mute the microphone, during a call (including a conference call), press the Mute key. The Mute key will glows red and the other parties can’t hear you.
To disable Mute, press the Mute key again.