This is a driver circuit for siren. This circuit usually used for car alarms. To build this circuit, we use VD-MOS FETs. This circuit receives 12 v supply from battery. A microprocessor sends complementary pulse waveforms to the driver circuit as inputs.  Here is the circuit :

Siren Driver Circuit circuit schematic

This circuit uses two PHC21025 which each of them contains two FETs. Two  BSN20 VD-MOS FETs in small SOT23 packages also used in this circuit. The maximum configuration of this circuit needs eight components and the minimum configuration of this circuit needs six components. [Source: NXP Application Note]