In an effort to reduce energy consumption, light bulbs are replaced worldwide with more efficient electric lamps. While to the consumer it is just a new product in an old socket, the differences in electrical terms are considerable - in contrast to conventional light bulbs, LED lights and compact fluorescent lamps ("energy saving lamps") are controlled by special electronic ballasts. These ballasts operate in part with switching frequencies up to 200 kHz and generate signal distortions at frequencies up to 1 MHz. The manufacturers are required to prevent detrimental circuit feedback and to ensure optimum service life of their products. To achieve the latter goal, a controlled warm start is often performed, which proper implementation in turn must be ensured by measurements.