turn it on & off 
automatic on/off
This feature automatically disconnects the speakerphone and turns it off when your phone is more than 20 feet away for more than 20 seconds (actual distance is network/ phone dependent). When you return and open the car door, the speakerphone turns on and tries to reconnect.
Note: Moving the speakerphone also turns it on.
To enable automatic on/off, just turn your speakerphone on and leave the Power switch in the center position.
Automatic On/Off
(Center) Position 
When your speakerphone turns on or off, you hear an audio tone.
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