An interface for a lamp operating device, in particular a ballast (EVG)
for gas discharge lamps, has two input side terminals of a digital
control input SE and a evaluation logic (AL) which is constituted for
processing both digital signals applied to the terminals and also mains
voltage signals. The amplitude of a mains voltage applied to the
terminals is continuously settable by means of a voltage divider (ST) or
a potentiometer. The amplitude of the applied mains voltage is converted
into pulse width information (PWM) which in turn the evaluation logic
converts into control commands, for example dimming setting values, for a
ballast (EVG).