Control system for railway car classification yard

Claim 1

IN A SYSTEM FOR CONTROLLING THE SPEEDS OF RAILWAY CARS ROLLING BY GRAVITY OVER A STRETCH OF SLOPING TRACK, A CAR RETARDER DISPOSED ALONG SAID STRETCH OF TRACK AND OPERABLE SELECTIVELY FROM A NONBRAKING POSITION TO A PLURALITY OF BRAKING POSITIONS, COMPUTER MEANS FOR PREDETERMINING A VOLTAGE ANALOG OF THE DESIRED EXIT SPEED OF SAID CAR FROM THE LEAVING END OF SAID RETARDER IN RESPONSE TO A PLURALITY OF FACTORS TO CAUSE SAID CAR TO ARRIVE AT A PREDETERMINED LOCATION BEYOND SAID RETARDER WITH A SELECTED SPEED, MEANS FOR SETTING UP A VOLTAGE ANALOG COMPARABLE TO A VELOCITY APPROACHING THE MAXIMUM VELOCITY THE CAR MAY HAVE AT THE ENTRANCE TO SAID RETARDER AND YET HAVE ITS SPEED REDUCED BY SAID RETARDER OVER SUBSTANTIALLY ITS ENTIRE LENGTH TO SAID EXIT SPEED, MEANS FOR STORING SAID VOLTAGE, RADIO FREQUENCY SPEED MEASURING APPARATUS EFFECTIVE TO PROVIDE OUTPUT PULSES WHOSE FREQUENCY IS RELATED TO THE SPEED OF EACH CAR PASSING THROUGH SAID RETARDER, CIRCUIT MEANS RESPONSIVE TO SAID PULSES FOR PROGRESSIVELY REDUCING SAID