PURPOSE: To remove ambient noise excepting for voice command starting sound by electrically connecting a second microphone to a speech identifying circuit so as to transmit a speech signal only when a first microphone generates a signal from a solid-state transmission sound. CONSTITUTION: The electric signals of the first microphone 2 to fix to the throat of an operator and the second microphone 5 facing the side of the mouth of the operator are supplied for a trigger circuit 10. The constantly open switch 10.2 of this trigger circuit 10 includes a timing element T closing the switch,10.2 after the lapse of the maximum receiving period of the speech identifying circuit to operate a signal transmitter. When the solid-state transmission sound is operated to the microphone 2, the switch 10.2 is closed by the operation of a threshold switch 10.1 and an amplified and filtered signal of the microphone 5 is transmitted to the speech identifying circuit as an output signal. Thereby actual ambient noise excepting for speech command starting sound can be removed.
展开▼
