| 摘要 |
PURPOSE:To detect a signal voice by good precision by removing a multi-frequency signal component detected at the time of the reception of a signal from an input signal, and obtaining the power value of the frequency component other than the multifrequency signal, and comparing the above mentioned power value with the power value of the input signal. CONSTITUTION:One direct current component is outputted respectively from two groups of detection circuits 41, 42 for a low group and a high group. The respective output signal groups of the detection circuits 41, 42 are sent to an output holding circuit 55 only when the output control circuit 59 of an output circuit 5 is set. In a voice detection circuit 7, the output signal of an input amplification circuit 1 is inputted, and further, sent to a band rejection filter 73 and a selection circuit 74 through the band rejection filter 71 and the selection circuit 72, and outputted to a power detection circuit 75. The power detection circuit 75 detects the power value extending over a prescribed period from the time of the detection of the multi-frequency signal. The outputs of the power detection circuits 75 and 76 are inputted to a comparator 77, and it decides whether it is the received signal or the voice signal or the multi- frequency signal, based on the largeness of a power ratio of the power of the signal other than the multi-frequency signal component against the total power. |
