Circuit diagram:Multitone Siren Circuit Diagram
These multi-frequency signals are mixed and fed to the audio amplifier built around IC LM386. The output of IC2 is fed to the speaker through capacitor C9. If you want louder sound, use power amplifier TBA810 or TDA1010. Only five outputs of IC1 are used here as the other five outputs (pins 4 through 7 and 14) produce ultrasonic signals, which are not audible. Assemble the circuit on a general-purpose PCB and enclose in a suitable cabinet. Regulated 6V-12V (or a battery) can be used to power the circuit.
Author: PradeeP G. - Copyright: Elektor Electronics Magazine