Figure shows the touch sensitive voice doorbell circuit. M is the Touch plate. This can be used in places wherever touch sensitiveness is required.
When anybody touches the plate, the signal goes to the trigger pin of IC 555. The IC gets triggered and it acts as a Monostable Multivibrator. With R2 and C2, it generates a pulse for 36 seconds. This pulse operates the IC2 – LH560, in which the recorded message “Please open the door” is there. The voice is then passed to the Loud speaker ‘B’ through the audio amplifier VT1. The recording voice and message can be changed and used accordingly.This circuit can also be used for security purposes.