Abstract: Alternating current track circuit energy for train detection and cab signals is coupled to the exit end of an insulated, dual gage track section between the common rail and the other two rails connected in parallel. The track relay is connected at the entrance end in a similar manner. Impedance bonds for direct current propulsion are also connected between the common rail and the other two rails at each end. In all forms, the propulsion return current is sufficiently balanced between the three rails to eliminate cab signal interference in either gage. In a first arrangement, a direct wire connection multiples the two other rails at each end. Impedance bond taps to complete the return circuit provide a two to one turn ratio from the common rail end of the bond winding to equalize the propulsion current ampere turns on each side of the tap and thus balance the flux generated.

Abstract: Separate traffic and block clear indication line circuits control either direction train movements through a stretch of track under cab signal indications without intermediate wayside signals. Reversible phase sensitive track circuits provide train detection and cab signal energy. A block clear, opposing locking repeater relay and a traffic route request relay at the selected entrance end of the stretch control the traffic line circuit to initiate traffic reversal operations. The magnetic stick traffic relays are shunted by a back contact of a neutral line relay to protect against lock out of the traffic line circuit by external voltage surges. The direction of the block clear line circuit is established by the traffic relay position. This second line circuit also checks the track sections unoccupied, the opposing signal, and traffic locking conditions before energizing a block or super-clear relay at the entrance end of the traffic stretch.

Abstract: A frequency selective filter is connected between the track transformer and phase selective unit at the receiving end of a coded phase selective track circuit to reject interfering signals of propulsion current frequency. The series L-C filter comprises a capacitor and a two-winding reactor coil with a resistor permanently connected in series between the two windings. Each winding is tapped to allow a selection of the filter inductance to match track circuit impedance, including impedance bonds and ballast resistance. Taps for short track circuits include the second winding and the resistor to improve signal to noise ratio. Energy for short interlocking track circuits is of a higher frequency, and a special tap on the first winding is selected to enable filter tuning at this other frequency for train detection since basic frequency is still used during code off-time for cab signal control.

Abstract: Data and voice communication links are provided between a movement direction center, a data processing center, and all mobile work units of a railroad terminal control system. A work assignment input from the movement direction center, e.g., an order to assemble a train, activates the data processing center to prepare and transmit to the selected switching locomotive an itemized work list, which is recorded in printed form at the locomotive to serve as specific instructions for accomplishing the assignment. The work unit crew reports readiness to begin and subsequent completion of each work list item. The data processing center responds to these and other information inputs, e.g., vehicle movement indications, to check the work done and to remotely establish the field conditions, e.g. track routes, necessary to accomplish the successive work items until the entire assignment is completed.