An electronic ballast with transformer interface communicating between an external control system and the electronic ballast comprises an outboard circuit (160) operably connected to the external control system and communicating with the external control system by an external signal (140); a transformer (162) being operably connected to the outboard circuit (160) and communicating with the outboard circuit (160) by an outboard signal (166); and an inboard circuit (164) being operably connected to the transformer (162), communicating with the transformer (162) by an inboard signal (168), and communicating with a micro-processor (128) by an internal signal (150). The external signal (140) can use the Digital Addressable Lighting Interface (DALI) protocol. The in board signal (168) can have a lower duty cycle and a higher duty cycle on the primary winding to generate a lower voltage and a higher voltage, respectively, for the outboard signal (166) on the secondary winding.