| 摘要 |
PURPOSE:To simplify the constitution of a tuning circuit and to attain the formation of an LSI by measuring the period of N periods of a signal to be measured and finding the frequency of the signal. CONSTITUTION:A control circuit 7 enters the output of a time measuring circuit 8 to a latch circuit 9 on the basis of an output obtained by collecting a sound through a microphone, amplifying a fine signal by a waveform shaping circuit 5, converting the amplified signal into a pulse string and counting the previously fixed number of pulses in a confirming circuit 6. The circuit 9 holds the measured value until the succeeding measuring data are determined. Thus, the period of N periods of the signal to be measured is measured and the frequency of the signal is found out from N/T by using time T. |
