Wailing Alarm Circuit Diagram. This alarm siren circuit produce warbling sound, you can use it in your toys or in security alarm. This circuit simulates the sound of an American police siren. IC2 is wired as a low frequency a stable that has a cycling period of about 6 seconds.
Wailing Alarm Circuit Diagram
The slowly varying ramp waveform on Cl is fed to pnp emitter follower Ql, and is then used to frequency modulate alarm generator IC1 via R6. IC1 has a natural center frequency of about 800Hz. Circuit action is such that the alarm output signal starts at a low frequency, rises for 3 seconds to a high frequency, then falls over 3 seconds to a low frequency again, and so on ad infinitum.