TANDBERG 550MXP - Manual (Page 33)

General Use
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3.2.4 Mic Off
To mute the microphone during a call, press the Mic off button. An on-screen indicator appears in
the upper right corner when the microphone is off. In a call, if audio is detected, the on-screen
symbol will start to flash. Pressing the Mic off button one more time will activate the microphone
again.
Note that Mic off will mute all microphone inputs.
When an incoming call is answered, the microphone may be in the off state because the Auto
Answer setting is On+Mic off, see
Auto Answer . The icon will start to flash when you start
speaking. Remember to turn the microphone on before a meeting.