The invention relates to an electronic ballast comprising a converter which is used to operate a discharge lamp, for example, a low pressure discharge lamp, for selectively operating, in a direct manner, the supply network or a phase section dimmer. Jumps in the supply voltage are decoupled by a differential which is connected between at least one of the network lines and the reference potential of the ballast and transmitted to a control of the ballast, such that the control of the converter can distinguish between the operation on the phase section dimmer and on the network supply.