A universal hand-free system for use with various types of cellular phones produced by different manufacturers is designed to operate in combination with a vehicle's audio stereo system. The hand-free system can automatically turn off a vehicle's audio stereo system when incoming signals are being received by a cellular phone and automatically turn on the audio stereo system as the cellular phone terminates its operation. It intends to improve the communication quality of a cellular phone and increase driving safety. Moreover, by means of signal cable, which can convert and discern incoming signals and signal criterion levels for various types of cellular phones produced by different manufacturers, the hand-free system can be universally applied to a variety of cellular phones.

A sound system for a motor vehicle and a method for defining a functional scope of a sound system include a control unit, an input unit for operating the system, a display unit, a unit for generating source data in the form of audio data, an amplifier unit for amplifying the source data, one or more speakers, and a bus system that assures transmission of the source data and control data for controlling the units among the individual units. At least one unit other than the control unit of the system has a memory assigned to it, in which the functional scope of that unit is represented. The functional scope can be transmitted through the bus to the control unit, and the transmitted functional scope can be used in the control unit for at least partially forming the functional scope of the entire system. The control unit, the input unit and the display unit are connected to one another in such a way that through the use of the display unit, operating menus required for operating the entire system can be shown in accordance with the functional scope of the entire system, and the operation of the system can be performed with the aid of the input unit on the basis of displays in the display unit.

Acoustic outputs from an audio system and various acoustic output devices are produced from a speaker, and a sound which a user desires to hear clearly is automatically selected and corrected with emphasis. A TV sound, an acoustic guide of a navigation system, and a sound on the other end of a hands-free device are delivered to a selector, and one of them is selected by a selector switching control and corrected by an acoustic correction filter to be produced. The other acoustic signals are produced as non-correction target signals together with an audio signal. An acoustic output processing control unit performs operational control of acoustic output processing corresponding to an operation mode of an acoustic output device and a present mode of acoustic output processing detected by device operation-mode detecting means while performing various operational function controls, including selector switching control and buzzer control, corresponding to data obtained by reading a memory in which modes of acoustic output processing are stored in advance.

An integrated mobile-phone handsfree kit combined with an existing vehicular stereo system utilizes the high power and high performance audio output characteristics to provide drivers with a safe, comfortable and high quality conversation environment in vehicle. The invention comprises an existing stereo equipment with loudspeakers, and an electric power module connected to the stereo equipment to share the same power supply. The stereo equipment has a sound output wire and an electric power supply input wire. The electric power module has a handsfree kit electric circuit assembly. The handsfree kit electric circuit assembly has a sound source selecting switch unit, a power amplifier, an earphone circuit, an audio fidelity processing unit, an electric power supply unit, a sound source control unit, and an electric power supply switch. The invention makes it possible to integrate the mobile-phone handsfree kit together with a vehicular stereo system to automatically detect the sound source(from stereo or mobile-phone) and then direct the audio signal to the loudspeaker output, and therefore simplifies wiring and eliminates the needs for extra power source and loudspeakers. The integrated handsfree kit also controls the loudspeakers in different locations by applying various output powers and phase delays for each loudspeaker in order to process the audio signal and simulate the sound fields as if the sound were coming from the front to allow drivers to concentrate on traffic while in conversation via mobile-phone.

An apparatus for use with a cellular telephone to indicate an incoming telephone call to a user includes a cellular telephone battery pack has a circuit that generates a voltage signal with a value representative of the current being drawn from the battery by the operation of the cellular telephone. A status determination circuit monitors the voltage signal and generates a waiting for call state signal whenever the value of the voltage signal decreases from a first selected higher value to a first selected lower value for a first preselected period of time. An incoming call detection circuit whenever the waiting for call state signal is present and either the voltage signal increases from a second selected lower value to a second selected higher value and remains at or above the second selected higher value for a second preselected period of time, or the current goes from a lower preselected current value to a higher preselected current value and remains at or above the higher current value for a third preselected period of time. An alarm is operative upon receipt of the alarm start signal for indicating an incoming call to a user. Also a cutoff circuit monitors the voltage of the battery and disables the apparatus further operation whenever the battery voltage drops below a preselected cutoff value to avoid damage to the battery.