This is a really simple. The IC UM3561 produces four differen sound effects, the output at Pin three being amplified by the transistor 2N2222. A 64 ohm loudspeaker can be substituted in place of the fifty six ohm resistor and 8 ohm loudspeaker.
The 2 pole four way switch controls the sound effects. Position 1 (as drawn) being a Police siren, position two is a fire engine sound, three is an ambulance and position four is a machine gun result.
