Complex sentence: The gear box that turns the top of the Post Office Tower in London was designed and built there and the electric motors that drives the gearing was manufactured by Brook (Electric) Motors, based in Brockholes.
Split into simpler sentences: The gear box that turns the top of the Post Office Tower in London was designed and built here. The electric motors that drives the gearing was supplied by Brook (Electric) Motors, based in Brockholes.