Hands-Free Microphone
In the head liner, two covers (1) for the hands-free microphone are mounted on the left and on the right close to the sun visors.
The hands-free microphone is always mounted on the driver's side, the right side cover is a blank (Right side cover is used for RHD vehicles).
The microphone is an active microphone with input sensitivity of 75 mV/74 dB.
Hands-free operation takes place via the microphone and the audio system via the ASK. The ASK provides the audio channels and switches off all other audio sources during hands-free operation.
This is a digital full duplex transmission. It means that the AF (audio frequency) is enabled for both parties (speaking and listening simultaneously in both directions). An echo compensation avoids feedback.
The hands-free microphone is also used for voice input for the Speech Processing System. In the telephone control unit, the analog signals from the microphone are converted to digital signals and forwarded to the SVS via the MOST.