The 90 centimeter Searchlight was powered by a Lister generator at 90 watts at 120 amperes to create a 2 billion candlepower focused beam of light out to 5 miles (8 kilometers). This model was installed in fixed fortifications, mobile trucks, and on ships for night defense. There were also 120cm and 150cm versions. Many women of the Auxiliary Territorial Service (ATS) were charged with operating these searchlights during air raids. The only all-female Royal Army unit operated 90cm searchlights.