| 摘要 |
PURPOSE:To reduce the quantity of hardware by providing a limiter circuit which performs Schmitt trigger operation to the output of an integrating circuit based on an upper-limit clamp value and a lowerlimit clamp value to generate a rectangular wave and a counting circuit which counts output pulses of the limiter circuit. CONSTITUTION:When a dial pulse signal is inputted, the integrating circuit 3 performs integration based upon the make duration of the dial pulse signal as a positive value and the break duration as a negative value and clips the upper limit and lower limit of the integrated value to certain values respectively to output the signal. The limiter circuit 4 which inputs the output performs the Schmitt trigger operation by using the upper-limit clamp value and lower- limit clamp value clamped by the integrating circuit 3. Then, a counting circuit 5 counts output pulses of the limiter circuit 4 and outputs the counting result to an output terminal 2. Consequently, a dial pulse receiving circuit which consists of a small quantity of hardware is obtained. |
