| 摘要 |
PURPOSE: A handsfree for a vehicle is provided to use a CDMA type mobile phone together with a GSM type mobile phone by removing a TDMA noise generated when using the GSM type mobile phone in a state of mounting one handsfree in a vehicle. CONSTITUTION: A microphone(10) converts voice signals of a driver into electric signals. The first amplifier(12) amplifies the electric signals. A mobile phone connecting part(38) is connected with an earphone jack of a mobile phone for receiving and transmitting call signals. A TDMA(Time Division Multiple Access) noise filter(40) removes a TDMA noise generated from a GSM type mobile phone. The second amplifier(16) amplifies the call signals from which the TDMA noise is removed. A memory(20) stores the pattern information of the noise. A DSP(Digital Signal Processor)(18) receives the voice signals for removing echo to output the voice signals to the second amplifier(16), and outputs audio signals by controlling the noise by comparing the noise pattern with the signals received from the second amplifier(16). An audio amplifier(22) amplifies the audio signals. A call switch(26) selects a call and an end, and selects a hands-free mode and an audio mode. A selector switch(30) switches audio output signals of a car audio(36) and the output signals of the audio amplifier(22). A control unit(24) controls the selector switch(30), and receives an amplification gain of the second amplifier(16) for automatically controlling a gain of the audio amplifier(22). A display lamp(28) displays a state of the control unit(24). A speaker(32) outputs the audio signals selected by the selector switch(30). An earphone(34) outputs the audio signals selected by the selector switch(30) exclusively from the speaker(32).
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