Abstract: Adjacent stations along a single track railroad without continuous train detection, are coupled by a communication channel over which distinctive signals requesting, acknowledging, accepting, and confirming completion of, train movements are transmitted. The operator at the departure station manually initiates the transmission of a first signal requesting a train movement to the adjacent station. The other station operator acknowledges the movement request by manually actuating the transmission of a second distinct signal accepting the move. The two signals jointly establish the requested traffic direction through the single track and clear the departure signal for the train. Occupancy of the single track by the train locks the channel to inhibit other movement requests, thus protecting the train while moving through the non-detection stretch. Arrival of the train at the far station is registered and confirmed by the operator who manually actuates the transmission of a train complete third signal.

Abstract: A route oriented interlocking control system with only entrance, exit, and alternate route selectors on the control machine console. No track switch controllers or indications are provided at the control location. Operation of entrance and exit selectors in sequence establishes desired route storage within the control machine, after the absence of any conflicting route and the non-occupancy of involved track sections are checked. This route control is then transmitted to the field location to select the field route relay, position the track switches, and clear the proper wayside movement indicator to authorize train movement through the route when all switches are positioned and the track within the interlocking is unoccupied. Indications of the registry of the route control and operation of the movement indicator are returned to the office display console. Route release occurs by secondary circuit controllers when the train occupies the final track section.

Abstract: A single relay serves to register route request selections for both traffic directions over each track route through a railroad interlocking layout. This single route request relay is jointly controlled by the route selection push buttons for both directions, the actuated push button being also repeated by a traffic direction relay. The route request relay pick up checks that no conflicting route request is active, and that the same or opposing route is not already established and locked. The route request and direction repeater relays are held by stick circuits to store the request until the route is locked. A single relay serves to provide the clear and lock function for all possible traffic routes originating at each entry point into the interlocking.