| 摘要 |
The circuit comprises a counter (13), a generator (11) that produces a reference signal (Sf) made up of pulses, and a two-input AND gate (10). One input of the AND gate is connected to the generator while the other input receives a signal (Sx) produced by a bouncing contact (X) as it switches from an open position to a closed position and vice versa. The output of the AND gate is connected to the clock input (C113) of the counter, which further has a reset input (R13) connected to the output of an inverter (14) whose input receives the signal produced by the contact. Opening of the contact causes the reference signal to be blocked by the AND gate and the counter to be reset. Closure of the contact causes the AND gate to open to the reference signal whose pulses then increment the counter and the latter, upon its contents reaching a predetermined value, issues an output signal (S13) in the form of a pulse. |
