Abstract: Step dimming of a fluorescent lamp load through sensing of power line interruptions generated through the toggling of a switch. The number of power line interruptions through toggling produced within a predetermined period of time identifies the level of dimming desired. In the event that interruption of power to the ballast exceeds the predetermined period of time, the lamp load will be reset to a prefixed level of illumination once power is restored.

Abstract: The invention relates to a circuit arrangement for operating a low-pressure discharge lamp. The circuit arrangement according to the invention comprises means X for supplying the low-pressure discharge lamp, provided with means X1 for generating a current of changing polarity. The circuit arrangement also comprises a feedback network which together with the means X and the low-pressure discharge lamp forms a control loop for controlling a lamp condition parameter. A low-pass filter is included in the control loop. The feedback network is provided with means M for generating a signal m which represents the instantaneous value of the lamp condition parameter, means C for comparing the signal m with a reference signal d, and means S for controlling the means X in dependence on the result of the comparison.