Delay electronic doorbell circuit a

When you press the doorbell
button, the sound will sound immediately. After you release your hand, the sound will continue for a
while.
    By adjusting the values ​​of resistor Rt and capacitor Cz,
the tone of the doorbell can be changed. By changing the capacity of capacitor C, the required
delay time can be obtained.
If a circuit as shown in Figure 13-25 (b) is added to the circuit, a jg-type door-smashing sting can be achieved.