Complex sentence: Westinghouse Electrical developed an electro-pneumatic multiple unit system that used a lower control current and when in 1903 the District Railway opened its line from Acton Town to South Harrow with experimental multiple units these used control systems from BTH and Westinghouse.
Split into simpler sentences: Westinghouse Electrical developed an electro-pneumatic multiple unit system that used a lower control current. When in 1903 the District Railway opened its line from Acton Town to South Harrow with experimental multiple units used these control systems from BTH and Westinghouse.