Abstract: A transmitter and a receiver are located at each junction location between adjoining track sections along a stretch of track for transmitting and receiving cab signal or speed control commands through wire loops laid in a preselected pattern parallel to and between the rails of each section. Train carried apparatus is selectively reponsive to the speed commands and to the pattern of the wire loops to control the movement of the train in the established direction through the stretch. A distinct directional frequency is transmitted from the selected entrance end of the stretch, when a train movement is desired, and is repeated at each wayside location through the wire loops to the exit end. The directional frequency reception at each location activates a filter output to selectively enable gating elements to connect the associated transmitter and receiver to the adjoining section loops in accordance with the desired traffic direction.

Abstract: A wire loop for carrying cab signal or speed control commands is laid parallel to the rails along the track center line except at the exit end of each section where an offset portion of this loop is laid immediately adjacent one rail to form a cut-in signal source. A second loop is laid along the center line of the rails through this offset distance, which is equal to the stopping distance of the train from the restricted speed rate, and each loop is supplied by the same cab signal transmitter. Each train carries receiver coils positioned above the center line loops and above the cut-in loop positions. The normal cab signal or speed control apparatus is controlled by the signal picked up by the receiver coil above the centerline loops in the track. A separate cut-in receiver is controlled by signals picked up from the offset portion of the main loop but responds only to a proceed signal command.

Abstract: In a railroad interlocking, a cab signal transmitter is coupled to the rails at each exit location and at such other locations as are necessary to supply continuous cab signal energy to trains traversing any possible route through the interlocking. Where train shunts prevent the reception of cab signal energy, wire loops laid adjacent the rails carry the cab signal energy for train pickup. Each rail coupled transmitter is finally activated to supply energy when a train occupies an associated track section. However, the control circuit network for each transmitter also checks, as pertinent for the established route, that a route has been established and the approaching train authorized to traverse that route, that any succeeding track sections along the route are unoccupied, that the transmitter for a preceding section has been activated, and that transmitters for opposing or conflicting routes are not active.