The first block is built on the NE555, which acts as a free-wave generator. VR1 50k potentiometer and C1 capacitor and VR3 100k potentiometer and capacitor C2 are responsible for the “rotation” speed. The VR3 potentiometer at maximum resistance... Electronics Projects, NE555 Super Siren Circuit "555 timer circuits, analog circuits projects, " Date 2019/08/04