Abstract: A railroad train moving along an approach to a grade crossing (or other location of interest) is detected by apparatus that is responsive to the change in effective track impedance caused by the moving shunt. A constant current AC signal is applied to the track adjacent the crossing, and the resulting voltage changed in amplitude and phase is picked off by a receiver on the opposite side of the crossing. Voltage and current information derived from these signals is inputted to a microcomputer which calculates the track impedance and determines whether or not a warning device or devices at the crossing should be activated. Such determination is made on a repetitive basis in accordance with a repeating program loop and stored in memory.

Abstract: The number of on-line locomotives of a consist is either reduced or increased by a manual control system that conserves fuel by throttling back trailing locomotives and operating the remaining locomotives of the consist at the most efficient throttle position. A control unit in the lead locomotive is operated by the engineer to command control units in equipped trailing locomotives of the consist. Each time the engineer depresses a "subtract power" push button, one trailing locomotive is throttled back; conversely, each time an "add power" push button is depressed, a trailing locomotive is returned on line by advancing its throttle to the most efficient position. A cutout control signal, which is generated in the lead locomotive and transmitted to trailing units in serial order (front to rear) by a single spare trainline wire, has voltage levels that progressively decrease or increase in response to the subtract or add power commands.

Abstract: An automatic speed control system for a consist of diesel locomotives conserves fuel by throttling back trailing engines and operating remaining engines at the most efficient throttle position. A control unit in the lead locomotive is operated by the engineer to command control units in equipped trailing locomotives of the consist. In the lead locomotive, depressing a "set speed" push button causes a speed memory to store the existing speed of the consist, and a cutout control signal is generated which is transmitted to trailing units in serial order, i.e., front to rear, by a single spare trainline wire. The control signal has two control voltage levels that increase or decrease with deviations of the speed of the consist from the desired speed in memory. These voltage levels are decoded by each trailing unit and, if power is needed, the engine throttle is set at the most efficient position or, if the locomotive is to be cut out, the throttle is set at a desired minimum position.