Lever frame; Westinghouse power frame, circa 1906

Early railway signals and points were operated by large levers, connected by wires to the equipment on the ground. Not only was this hard work for the signalman, but the levers took up lots of space. During the 1900s compact lever frames such as this were adopted for use on London's tube lines, then being built. The wooden cabinet houses the mechanical interlocking gear that prevents points and signals being set in dangerous combinations.