Ballasts contain step up transformers and ignition circuitry ballasts are also available with combined timers these timers use relays and are rated for high load unlike cheap external timers with our range of ballasts both high pressure sodium hps and metal halide mh lamps can be interchanged all ballasts listed here are suitable for all use with all high pressure sodium hps and metal halide mh lights shown here for questions regarding ballasts and cabling please contact esoteric