A starting circuit for an electric discharge lamp providing an electric
current to a lamp having a first and a second filament. The circuit
measures a lamp current and a filament temperature and then compares
these against a reference voltage. When the lamp current is below a set
threshold value, a relay contact disposed between the first and second
filament is closed to direct the electric current through the first and
second filaments to initiate pre-heating of the lamp. Once the filament
temperature exceeds a set threshold, the relay contact is opened and the
electric current passes through heated gas inside the lamp.