Digital answering machine timing circuit

 (1) Introduction to the circuit principle: The program host sets the time for an answer according to the difficulty of the answer question, and presets the counter
through the preset time circuit. The clock pulse of the counter is provided by the second pulse circuit. The preset time circuit is designed using the 741.S192 decimal synchronous alkali adding counter .     (2) Component parameter selection The selection of components is shown in Figure 3-26, and there are no special requirements.   '(3) Digital responder timing circuit is shown in Figure 3-26.