This siren alarm circuit diagram is based on a specialized IC UM3561, which is a low power CMOS LSI specially designed for this type of applications. The UM3561 contains all needed parts ( oscillator, selector circuits, programmed mask ROM ) to simulate siren sound using few external components. The siren circuit require a power supply circui
t around 3 volts and has a low current. The UM3561 siren sound generator circuit has possibility to generate four types of sounds : police siren, fire engine siren, ambulance siren and machine gun sound.