JPS6418391A - Control system for intermittence of audible signal tone - Google Patents

Abstract

PURPOSE:To eliminate the generation of the discontinuous point of a signal and to prevent high frequency noises from being generated by storing data in a data storage memory while an audible tone deviates in frequency so that the data value of a sample at the on-off switching point of an intermittence period is zero. CONSTITUTION:The data storage memory 11 is stored with the data which deviates in the frequency of each audible signal tone previously so that the data value of the sample at the on-off switching point of the intermittence period is zero. Namely, the sample data of the signal tone in the period where the audible tone signal whose frequency is nearly fi has time length T (time width of the on state of the audible signal tone) is stored in addresses 0-P of the memory 11. Further, the data is stored while given the shift so that the data value of the sample at an end point (on-to-off switching point) is zero. Therefore, a read control circuit 10 begins to read the data at the address 0 of the memory 11 and when zero is outputted as the sample data, an intermittence control circuit 12 which synchronizes with it turns off the output of the signal tone. Consequently, the discontinuous point of the signal is eliminated and high frequency noises are prevented from being generated.