RAILROAD CONTROL SYSTEMS CONSISTING OF CONTROL PANELS, WIRE BASED AND RADIO BASED CONTROLLERS, COMPUTERS, PRINTERS, MONITORS, INPUT/OUTPUT DEVICES, NAMELY SIGNAL RELAYS, SIGNAL CONVERTERS, MICROPROCESSORS, DISCRETE INPUTS/OUTPUTS, TRACK CIRCUITS, SIGNAL LAMPS, FIELD DETECTORS, AND CROSSING WARNING SENSORS AND DISPLAYS; SWITCH MACHINES; AND COMPUTER SOFTWARE TO CONTROL RAILROAD SYSTEMS
Electrical and Scientific Apparatus