Two fluorescent lamps connected in series are operated with just one Ballast. Since each lamp only receives half the voltage, a 110 V starter must be used with each lamp. This type of circuit is only suitable for use with the following lamp-ballast combinations:

Lamp Length [mm]
T16 4W 136
T16 6W 212
T16 8W 288
T26 15W 438
T26 18W 590
T38 20W 590
TC-L 18 W 225

The circuit is not compensated. If ignition time for luminaires on a tandem circuit is too long, simply reverse the polarity of one of the starters (turn the starter through 180° and replace).