806,091. Controlling burners. LANDIS & GYR A. G. March 3, 1955 [March 3, 1954], No. 6319/55. Class 75(1) [Also in Group XL(b)] In a supervisory arrangement having a rectifying impedance as a sensing means, the impedance is connected into the ignition electrode circuit of a glow discharge tube 7 and the ignition electrode circuit has at least one capacitor 11 the charging of which takes place only during the negative half cycles of an alternating current potential applied to the anode 6 of the discharge tube. The arrangement shown is used in a burner installation, the rectifying impedance being a photo-electric cell 23 sensitive to the luminous flame of a pilot burner. The arrangement is such that if a flame exists at the pilot burner a relay 8 in the anode circuit of the discharge tube is energized and operates contacts to maintain open a regulating valve supplying a main burner. The capacitor 11 is connected to a tapping 28 on the supply transformer between the anode terminal 3 and a further tapping 5 connected to the cathode 10. The anode voltage of the photo-electric cell is in antiphase with the anode voltage of the discharge tube. When the photo-cell is illuminated by the pilot burner flame the condenser 11 charges on the half cycles when the anode voltage of the photo-cell is positive, and during the alternate half cycles a relatively small discharge of the capacitor 11 takes place through a resistance 14. Consequently a voltage builds up on the capacitor 11 to bias the ignition electrode 13, positively. Ultimately this bias voltage and a positive half cycle of the alternating voltage applied to the ignition electrode 13 are sufficient to start a discharge between the ignition electrode and the cathode 10. The main discharge between anode 6 and cathode 10 then follows and energizes the relay 8. The anode current is smoothed, so that the relay remains energized during the half cycles when the anode 6 is negative, by a dry rectifier 9 or by a condenser. Alternatively a slow release relay may be used. The relay 8 may open a contact 29 in the circuit of the resistance 14 so that the small discharge of the capacitor 11 between charging half cycles is. prevented. The capacitor 11 is connected in series with a smaller capacitor 12 which is bridged by a resistance 15. A limiting resistance 25 is connected in the circuit of the photocell. Fig. 3 (not shown) shows a similar circuit using an electrode in the flame of the pilot burner as the sensing means and a glow discharge -tube of the type in which the discharge between ignition electrode and cathode is initiated by a negative voltage on the ignition electrode. The cathode tapping on the supply transformer is located between the anode and ignition electrode tappings. The anode tapping and the pilot burner are earthed. A photocell may be used as sensing means instead of an electrode in the flame.