Abstract: An incandescent lamp has an attachment for connection to a two-wire electrical power line and a bulb containing a radiating element. At least two filaments are housed in the bulb and constitute the radiating element, and circuitry has an input connected to the electrical power line and an output connected to filaments. When a selection signal indicating the desired brightness is passed to circuitry, preferably along the electrical power line, and acts in such a way that circuitry selectively provides a feed to filaments on the basis of the selection signal, a change in brightness is obtained without deterioration of the color characteristics because the filaments operate under their rated operating conditions. The change in brightness will not be continuous, but discrete, but is more than acceptable for domestic requirements even with a small number of filaments.