Abstract: At a railroad crossing, a single motion detection unit is selectively coupled to an occupied track in such manner that safe, effective and efficient control is obtained over the crossing alarm device. The means for coupling the motion detection unit includes means for terminating the activation of the crossing alarm device when a train stops on the approach track, but short of the actual intersection. Techniques for multiplexing a motion detection unit with plural tracks at the grade crossing or with multiple track circuits on a single track are provided. Safe operation is assured with multiple track occupancy irrespective of the sequence of occupancy and which is the last to remain occupied or if one of the trains stops or reverses direction of motion.

Abstract: A highway crossing warning system includes a motion detector transmitter and receiver respectively coupled to the track rails adjacent the highway crossing for detecting motion of an approaching train. Wrap-around approach sections initiate operation of the highway crossing warning, but once motion is detected, the motion detector can serve to inhibit the highway crossing warning, after a predetermined delay, if motion indication ceases. To increase the effectiveness of the motion detector, the motion detector transmitter impresses a modulated carrier onto the track rails, wherein the modulation is phase locked to the carrier. The receiver, tuned to the carrier frequency, detects the modulation, and then determines from the level of the modulated signal whether or not approaching motion is detected. The transmitter employs solid state circuits switched between saturated and off conditions to prevent circuit component failures from masking approach motion.

Abstract: A control system including apparatus for the transmission of information for the control of vehicles travelling in one direction on a guideway. The guideway is broken down into a plurality of groups of uniquely identified sequential blocks. Each block has at least one vehicle detector for detecting the presence of a vehicle and having an operated condition responsive to vehicle detection. Each block further includes a transmitter for providing, to a vehicle within the block, information concerning the block it is in as well as information regarding the identity of the next downstream occupied or unavailable block. To this end, each block has associated with it a word generator for producing a signal identifying the block; the word generator is coupled to the block transmitter, which transmitter is only enabled when the vehicle detector is in its operated condition.

Abstract: Method and apparatus for detecting the presence of flat wheels on railroad cars, comprising an electro-acoustic transducer located on the track wayside so as to pick up the vibrations generated by a passing train. If a flat wheel is present it will generate a periodic clanging sound at a frequency proportional to train speed and wheel diameter. The invention capitalizes particularly on the measurement of train speed to control the response of an adaptive filter so as to enhance the periodic clanging frequency with respect to the background noise, thereby to improve the signal-to-noise ratio; the enhanced signal is further autocorrelated for ten wheel revolutions and if a periodic signal is present in the narrow frequency band of interest, a large periodic autocorrelation output will result and, as a consequence, any wheel flat will be readily detected and will act to trigger an alarm to alert the train crew of the condition.