HandsFreeLink System Description - Overview
The HandsFreeLink® (HFL) automatically connects (pairs) to a linked phone when the vehicle is in the ACCESSORY or the ON mode. The HFL also synchronizes with the paired cell phone's phone book to automatically update any changes. Depending on the functions of the cell phone, the automatic update may not work.
HandsFreeLink Control Unit
The audio unit or the audio-navigation unit builds in the HFL circuit, HFL microphone*1, and the Bluetooth transceiver. The HFL switch*2 controls the HFL function using the hard wire.

*1: With normal audio
*2: With display audio or color audio
Diagnostic Function (Without Normal Audio)
The audio unit or the audio-navigation unit can check the HFL components by the System Diagnostic Mode.
Checks the connection between the audio system and the internal Bluetooth module.
Checks the status of the HFL switch detection.
With display audio: Checks the voice input level of the HFL microphone.
With color audio: Checks the connection between the audio unit and the HFL microphone.
General Operation
The HFL switch on the steering wheel is used to answer incoming calls, to make outgoing calls, or to end a call. The signal is sent to the audio unit or the audio-navigation unit.

The microphone picks up the driver's voice, and sends the signal to the audio unit or the audio-navigation unit. The signal is then sent from the Bluetooth transceiver to the cell phone.

The caller's voice signal is sent from the cell phone to the Bluetooth transceiver. The audio unit or the audio-navigation unit outputs the voice signal through the front door speakers.
Muting Logic
When you are talking on the cell phone using the HFL, the front speakers provide the HFL sound and the rear speakers are muted.
Voice Control Function (With Display Audio)
The audio unit or the audio-navigation unit has voice recognition function about the HFL. Using the TALK button on the steering wheel to activate the voice control, the customer can make a call by talking a number or a contact name. As for vehicles with navigation, the audio-navigation unit controls the HFL by the navigation voice control.
Voice Tag Function (Without Normal Audio)
The audio unit can save voice tag to memory for making a call by voice recognition possible. The voice tag saved at the audio unit is related with Speed Dial.

Fan Mute Operation (With Climate Control)
When the voice recognition is in use, the audio unit or the audio-navigation unit sends the fan mute signal to the climate control unit via the B-CAN. The blower fan operating voltage may be reduced depending on the current fan speed.
Short Message Service (With Display Audio)
The audio unit or the audio-navigation unit processes the short message service (SMS) data sent from the cell phone. The text message information is displayed on the display.
HFL Microphone
The HFL microphone receives voice command or HFL speech, and transmits them to the audio unit or the audio-navigation unit.

Array Microphone (With Display Audio)
The microphone unit consists of two microphones. These microphones detect the driver's voice and the passenger's voice separately.

The HFL microphone is switching the directivity by the voltage change on HFT MUTE line.

 
Description
HFT MUTE Signal
HFL/NAVI voice recognition mode
When using the HFL voice tag function that is embedded into the audio unit or the audio-navigation unit, the directivity range becomes the driver's side and front center area.
0 - 1.5 V
HFL telephone mode
When using the HFL via the audio unit or the audio-navigation unit, the directivity range becomes the driver's side and front passenger's side.
3 - 5 V
Server voice recognition mode
When using the voice recognition system via an external device (like smartphone), the directivity range becomes the driver's side and front center area.
7 - 9.5 V