| 摘要 |
PROBLEM TO BE SOLVED: To prevent the occurrence of hauling phenomenon with a simple circuit configuration by providing an inverting circuit for inverting an output signal from a delay circuit, and an adder whose output terminal is connected with a telephone set body for adding an output signal from an outside microphone to an output signal from an inverting circuit. SOLUTION: A received voice S2 outputted from an outside speaker 13 is inputted to a sound collecting microphone 15 as it is. This voice S2 is converted into a voice S2' by a delay circuit 16, and then turned into the inverse of the signal S2' by an inverting circuit 17, and inputted to an adder 18. On the other hand, an output signal from an outside microphone 12, that is, a conversation sound S1 of a driver DR and a received voice S2' from the outside speaker 13 are inputted to this adder 18. Therefore, the voice signal S2' can be cancelled, and the output signal of the adder 18, that is, a transmission signal to be outputted to a telephone set body 11 can be a voice signal S1 of the driver DR from which the received voice S2' from the outside speaker 13 is removed.
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