Muting
To Mute the Microphone:
During a call, press the (mute) button. The button will turn red and a red microphone will show up on the phone's screen.
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To Un-Mute the Microphone:
Press the (mute) button again. The button will no longer be red, and the red microphone icon will disappear from the screen.
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To mute the phone ringer, see Setting Ring Volume