Voice Output With Hands-Free Mode
In hands-free mode, high-frequency signals received by the GSM antenna and transmitted to the NAD/GSM 900/1800 module (transmitter and receiver module) for the GSM mobile phone network 900/1800 MHz in the Telematic Control Unit (TCU). From this module, the high-frequency signals, with the voice information contained in them, are transferred to the MUX-DSP module. The MUX-DSP module is an electronic switch and converter and fulfills the following tasks:
- The multiplexer (MUX = electronic switch) switches the channel for the voice output and input.
- The digital sound processor (DSP) converts the high-frequency signals with the voice information into low- frequency signals.
The low-frequency signals are converted by the loudspeakers into sound signals and transmitted to the vehicle interior.
- The incoming call is accepted when you press the transmit/receive button on one of the following displays:
- On-board monitor
- Multi-information radio
- Multi-information display
- Central information display
- BMW Professional radio
- BMW Business radio
- A radio which has been switched off is switched on by a switch-on signal for the telephone conversation.
- If a radio is switched on, a signal is send to the radio mute (mute signal) in the audio system (music, CD, etc.) to mute it.
- At the same time as the radio is muted, a ringing tone is output through the audio system to indicate an incoming call. High-frequency signals are sent via the MUX-DSP module to the audio system to produce audible signals. The loudspeakers in the audio system convert the low-frequency signals into a single signal sequence and emit these into the vehicle interior.
- Hands-free mode is activated and the hands-free facility with digital full duplex transmission (the people in the conversation can speak and listen simultaneously) is activated via the MUX-DSP module.