This siren configuration found in a documentation from the 1980s can also be seen in many of our projects and in this circuit bank. Transistors are common, but Q2 can be of power for a higher voltage supply.
This circuit is from the SGS manual of linear integrated circuits of 1982. The L78xx is equivalent to...
We found this circuit in a 1965 General Electric manual. The circuit applies to incandescent bulbs...
This circuit causes a set of LEDs to flash sequentially in a move that is modulated by the audio...