Fluorescent lamp ballast with selectable power levels

In combination with a lamp circuit including a fluorescent lamp having first and second cathodes with resistive-heating filaments each spaced at a respective end of a lamp tube;

• first and second power leads for respectively connecting said cathodes to an a.c. power source whose power can be selectively enabled and interrupted by a main power switch;
• and a ballast inductor being in serial circuit with one of said power leads and including a plurality of filament-heating windings for supplying power to said cathodes;
• a power-level selection circuit interposed between a first cathode and a filament-heating winding, comprising:
• (a) a power-receiving circuit coupled to said filament-heating winding to receive power therefrom;
• (b) a filament-supply circuit for continuously supplying available power to said first cathode;
• and
• (c) a selectable-impedance circuit serially being coupled between said first power lead and said first cathode and being responsive to repeated, predetermined durations of interruption of power from said a.c. source to said power leads for toggling between a first and a second impedance of said selectable-impedance circuit, thereby providing two different power levels of said lamp.

For use in combination with a lamp circuit including a fluorescent lamp having first and second cathodes with resistive-heating filaments each spaced at a respective end of a lamp tube;

• first and second power leads for respectively connecting said cathodes to an a.c. power source whose power can be selectively enabled and interrupted by a main power switch;
• and a ballast inductor being in serial circuit with one of said power leads and including a plurality of filament-heating windings for supplying power to said cathodes;
• a power-level selection circuit interposed between a first cathode and a filament-heating winding, comprising:
• (a) a power-receiving circuit coupled to said filament-heating winding to receive power therefrom;
• (b) a filament-supply circuit for continuously supplying available power to said first cathode;
• and
• (c) a selectable-impedance circuit serially coupled between said first power lead and said first cathode and being responsive to a predetermined duration of interruption of power from said a.c. source to said power leads for selecting a different impedance of said selectable-impedance circuit, thereby selecting a different power level of said lamp.