This AC 220V siren circuit is a simple siren that use 220V AC as power supply. It is small size and use a piezo speaker cause use low power and saving.
I like to build simple audio alarm circuit using transistors. Although it is old circuit, it still useful. It uses just two transistors, other components.
This is police siren circuit using 555 IC, with PCB layout, using 2 IC-555 as frequency oscillators and transistor to drive sound to the speaker [...]
This is simple Warble tone generator circuit , use scr as main of oscillator and signal will be boost, then feedback to SCR again. Output is 32 ohms speaker [....]
Suitable for beginners. Build a simple, but widely applied.