| 摘要 |
PURPOSE:To prevent the mis-correction due to noise, by discriminating the magnitude of received audio signal before the detection operation of received time casting signal and automatically adjusting the threshold value of peak discrimination circuit producing the pulse in response to the received time casting signal. CONSTITUTION:When the content of the counter of the watch circuit 7 is e.g., 6:59'30'', the AND gate is opened. When the received input sound pressure is greater, the audio signal with attenuation such as 500Hz other than 400Hz time casting predict tone through BPF3 via the amplifier 2 triggers the peak discrimination circuit 4, the output pulse of the circuit 4 is counted at the counter CUNT, and the counter CUNT produces a given value of arrival signal before the time casting tone is received. Thus, the switches SW1, SW2 are selected, the threshold value of the circuit 4 is automatically greater with the resistor R2 corresponded, the circuit 4 is not triggered with noise, and miscorrection of time due to the time casting signal discriminating circuit 5 and time correction circuit 6 by noise can not be made. Further, it is the same with the adjustment of the gain of the amplifier 2. |
