Abstract: With a triac placed in series with a load, a threshold detector feeds a modulator supplying a pulse with a given delay with respect to a change of condition of the threshold detector. The output of the modulator is fed through a gate and a monostable flip-flop to the gate electrode of the triac. After the first gate pulse, if the threshold detector detects another voltage rise at the terminals of the triac during a period of time determined by a second monostable flip-flop, this change of condition causes, through an AND gate, the OR gate and the first monostable flip-flop, another pulse to be supplied to the gate electrode of the triac. The result is an increase in the reliability of triggering a triac and reduction in the consumption of the control circuit.