This circuit is from a 1967 publication, but it can be implemented with any Triac of the TIC series and the diode can be 1N4004. In position 1 the circuit is off, in 2 the load receives half power and in 3 the full power. The triac must be equipped with a heat radiator and the circuit also works on the 220 V power grid, being connected in series with the controlled load.
