false triggering of scr q3 due to rate effect diode d3 acts as a catch diode allowing capacitor c4 to charge its return path being supplied through diode d5 and put q4 capacitor c4 is now charged to a high value e g in the 100 volt range diodes d3 and d4 prevent this charge from being conducted back to the supply rail through choke l1 and resistor r5 capacitor c3 has recharged to a level exceeding the gate bias on put q2 again triggering the latter into forward conduction capacitor c3 and resistor r4 again supply current through put q2 triggering scr q3 which provides a low impedance path for the left hand side of capacitor c4 thus the high voltage on capacitor c4 is discharged through diode d6 the primary of transfomer t1 and scr q3 this discharge produces a large current spike in the primary of transformer t1 this energy is magnetically coupled to the secondary of transformer t1 producing a high voltage in the secondary winding the high voltage thus present at electrode device 16 produces an arc in the region of the unlit pilot gas diode d2 provides the return path for the seondary current of transformer t1 diode d5 suppresses ringing in the primary winding the aforedescribed circuit operation is thus in the nature of a capacitive discharge device powered by a flyback pulse converter the latter is formed by choke l1 diodes d3 amp d4 resistor r5 r6 r7 r8 and r10 scr q3 put q4 and capacitor c4 when the pilot gas is relit the low impendance path provided by flame 14 reduces the voltage at the base of transistor q1 preventing capacitor c3 from charging to a.