This circuit is a circuit that sounds a siren-like sound of ambulance sirens. This circuit is different to an ambulance siren circuit generally, is to use transistors instead of IC 555. Which allows economical and easy to tailor a network.
Operation of the circuit. This cycle can be divided into three main parts is the low frequency production. Production of high frequency. The amplifier.
The manufacture low-frequency includes Q1(C458), Q2(C458), R2, R3, C2, C3. Which will produce low-frequency out and to extend the Q3. Before you sent with high frequency of origin from Q4(C458), Q5(C458), R8, R9. , C5, C6 signal is included, then the output will come out to the leg E of the Q5(C458). and then be expanded with Q6(BC337) to drive the speakers. The C1, C4 is intended to stir filter collects them. The R11 will help prevent speaker damage.
Transistor Q1-Q5, you can use very many number that is NPN 100mA current collector. For example :
2SC1815 or 2N2222 or 2N3904 etc.