This well-known circuit version of the siren was obtained in a Colectro Handbook from the 70s. The transistors are of general use, with Q2 being a BD136 for greater power with power from 6 to 12 V.
This circuit generates a frequency modulated tone with excellent power. Other power MOSFETs can be...
This circuit has a sensitivity of 200 mV providing an RMS power of around 4 W for a load of 8 ohms...
This filter was obtained from Radio Electronics from the 80's. The configuration applies to any...