In 1940, the station was electrified and the lamp was replaced with a 1000 watt electric bulb, and the incandescent oil vapor lamp was moved to Au Sable Point Lighthouse in Northern Michigan. Split Rock was upgraded with a fog signal housed in a building next to the light tower. The original signal was a pair of sirens driven by two Franklin gasoline-driven air compressors manufactured by Chicago Pneumatic Tool Company. In 1932 the gasoline engines were replaced with diesel engines. The steam sirens were replaced with a Type F-2-T diaphone (be-you) type signal in 1936. The station and the fog signal were electrified four years later, but discontinued in 1961.