Railway signal systems, hearing before subcommittee, 74th Congress, 2d session, on H. R. 2748, to promote safety of employees and travelers on railroads by requiring common carriers engaged in interstate commerce to install, inspect, test, repair, and maintain block signal systems, interlocking, highway grade crossing protective devices, automatic train stop, train control, cab signal devices, and other appliances, methods, and systems intended to promote safety of railroad operation, Mar. 4, 1936.