In 1898 the Waterloo & City Railway opened to the public using electric multiple units. Each four-car train had two trailers and two motor-cars with two motors that could be directly controlled from either car. A four car train seated 204, and access was by sliding doors at the car ends leading to a platform protected by a gate. When the Central London Railway opened in 1900, carriages were hauled by heavy electric locomotives that caused vibrations that could be felt on the surface. In 1903 sixty-four motor-cars were delivered and the carriages were reformed into multiple units using a control system developed by Frank Sprague in Chicago. Initially there were 168 carriages, each long, with access via sliding doors to a gated platform as on the Waterloo & City. Seating was mostly longitudinal for 48 passengers and straps were provided for those standing. The Great Northern & City Railway was a built to take main line trains from the Great Northern Railway (GNR) at Finsbury Park to the City at a terminus at Moorgate. However the GNR refused permission for trains to use its Finsbury Park station, so platforms were built beneath the station instead. Public service on the line began in 1904, using larger electric multiple units with control equipment supplied by British Thomson-Houston. The Underground Electric Railways Company of London (UERL) had been established in April 1902 by the American Charles Yerkes to build and run three cross-London tube lines: the Charing Cross, Euston and Hampstead Railway (now part of the Northern line), Baker Street and Waterloo Railway (Bakerloo line) and the Great Northern, Piccadilly and Brompton Railway (Piccadilly line). A power station capable of providing power for these tube lines was built at Lots Road, by Chelsea Creek. Similar electric multiple units were purchased for the three lines, controversially from America, France and Hungary, and known as "Gate Stock", as access to the cars was via lattice gates at each end. Motor cars, trailers and control trailers were coupled to make a train of two to six cars, with the motor cars positioned at the outer ends. These had full width control compartments behind the driver and seated about 40, whereas the trailers seated about 50. A gateman operated the lattice gates using a crank handle and announced each station as the train approached. A bell rung by the rear guard when all gates were closed was echoed down the train by each gateman until the front guard signalled the driver to proceed.