BMW Bluetooth Upgrade Module Owner's Manual page 6

Overview
Bluetooth wireless technology is a short range radio
®
frequency, where signals are transmitted through the airways.
Hands-free system
The hands-free microphone is located either in the head-
liner or on the steering column depending on your vehicle.
The hands-free system is switched on automatically when
you make or receive a call using the following equipment:
Button on the steering wheel
Control display
Onboard monitor*
Multi-information display (MID)
As soon as you make a call with the hands-free system, the
other audio sources are automatically muted.
Adjusting the volume
You can adjust the volume of the hands-free system during
a phone call:
by using the buttons on the multi-function
steering wheel.
by using the volume control knob on your onboard
monitor, MID or radio.
The volume of the hands-free system stays at the level set
here even if you lower the volume of other audio sources to
a minimum.
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