US Patent 7109668 Electronic lighting ballast

An electronics enclosure has a mains input and a lamp output. A power factor correction circuit is installed in the enclosure, to provide a DC output voltage. An inverter is also installed in the enclosure. Control electronics is also installed in the enclosure to control the inverter, and to receive a selection of lamp load type made manually by a user via a user interface on an outside face of the enclosure. The same lamp output can thus alternatively drive, for example, a high pressure sodium lamp and a metal halide lamp, as indicated by the selection. Other embodiments are also described and claimed.