 The electrical installation provided 800 volts DC to power arc lamps in the engine and boiler rooms and Swan incandescent bulbs in other parts of the ship.The circuitry was complicated because the lighting consisted of sets of 18 Swan lamps and an arc lamp arranged in series.Each incandescent bulb was fitted with an automatic mechanism to switch in a resistor to maintain continuity should it fail, so that the set of 19 lights would not be extinguished if one failed.