Toy Siren Circuit Diagram

This simple Toy Siren circuit for hobbyist and student who game liker, this is a very simple Toy Siren circuit,  This Toy Siren circuit can be built small enough to frt inside a toy. The Toy Siren circuit consists of a relaxation oscillator utilizing one uni-junction transistor (2N2646, MU10, TIS43). R2 and C2 determine the frequency of the tone. 

Pushing the button, SW1 charges up the capacitor and the potential at the junction of R2 and C2 rises, causing an upswing in the frequency of oscillation. On releasing the push-button the charge on C2 will drop slowly with a proportional reduction in the frequency of oscillation. Manual operation of the button at intervals of approximately 2 seconds will produce a siren sound.