| 摘要 |
PURPOSE:To attain a data input by a dial telephone set by detecting the impulse response of a dial number. CONSTITUTION:An A/D converter 1 converts the impulse response generated by rotation of a dial into a digital signal. An analyzing circuit 2 analyzes the A/D converted output and outputs a cyclical pulse signal (b) showing the rise and fall of a dial pulse (a). A pulse counter 3 is constituted of a bilateral counter, acts so as to subtract one from its counting value with the aid of the signal of a time detecting circuit counting the break period of a pulse when it detects the next pulse before it counts the prescribed time (about 33msec), and does not count the pulse showing 'make' or a noisy pulse. The time detecting circuit 4 counts each break period and simultaneously counts the time from beginning to end of the dial pulse. When the counter output and the time output corresponding to said output can be available from the time detecting circuit 4, a deciding circuit 5 outputs the counter output as a dial number. |
