Schematic shows the "Lead / Lag" type of Ballast used with single pin Fluorescent lamps for Cold Cathode emission [operation].
One lamp is Leading the other one due to Reactance. The Reactance is from the Reactors [Choke coils] and the Capacitor. The lamp with the Capacitor will have the Lead effect on the Current wave, where as the lamp with only the Reactor will have the Lead effect on the Voltage wave.
This method allows the lamps to be started without heating the fillaments - hence the circuit is almost the same as the preheat Ballast's circuit; only here there's no starter[s] and only one connection to the filaments at each end of the lamp.
Scott SET posted 07/20/2001