A discharge lamp lighting method for controlling lighting of a discharge lamp includes varying an amount of generation of overshoot and undershoot generated in a waveform of a drive current that is applied when driving the discharge lamp, according to a magnitude of drive power supplied to the discharge lamp and a drive mode. Each input pattern array has a plurality of input vectors, while each input vector represents a time point and has input values representing a plurality of parameters indicating the current condition of the object. The combined housing latch and shorting member is latched behind a portion of the housing to retain the first contact terminal to the housing. Rather, the microprocessor-based control system employs software that replaces the control hardware, and directly reads the inputs, calculates the control actions, and writes the outputs. The module is normally mounted within a unit rack, and thus, can have a removably attachable, and re-orientable keyed surface on its rear face which mates with a corresponding keyed surface on the interior surface of the unit rack. A synchronization mechanism is provided that synchronizes the movement of the upper and lower vehicle chains.