The Invention of the Track Circuit / The history of Dr. William Robinson's invention of the track circuit, the fundamental unit which made possible our present automatic block signaling and interlocking systems

by American Railway Association

This being done, the first train that passed connected the opposite rail lines through the wheels and axles, short circuited the relay, thus operating all the signal circuits under its control, thereby practically demonstrating the feasibility of the system. This was in 1872. This block was extended to the agent's station over a mile from the signal, at which station the track battery was placed and also a switch for the manual operation of the signal, and also an overlapping telltale signal showing to the agent when the distant main signal was actually exposed at danger. The signal also indicated to the agent the approach of a train when a mile away.

Another installation was immediately ordered to be made at Irvineton on the same road. This was completed early in 1873 and worked perfectly from the beginning, performing all the functions described in connection with the installation at Kinzua. The locomotive engineers were greatly interested and soon christened the Irvineton signal "The Old Reliable." This was followed by other installations on this road and in 1873 Mr. Robinson had made installations of his closed rail circuit system of signaling on four different railroads, followed by various installations on many other railroads in the following years, as he was the sole owner of the system for about nine years, that is, until about 1880 or 1881, when the Westinghouse people obtained control of the system by the purchase of Robinson's interests. This was promptly followed by a reorganization under the name of the Union Switch and Signal Company, the terms "Union" and "Signal" representing the Robinson interests in the reorganization. This company thus became the sole owner of the Robinson Closed Circuit System of signaling until the expiration of his patents, when all other signal companies adopted the Robinson system as the basis of their signal work.

The original name of the Robinson Company was The Union Electric Signal Company, which Robinson organized and owned in 1878. In the reorganization the word "Electric" was canceled from this title and the words "Switch and" substituted, thus forming the present title: "The Union Switch and Signal Company."

Rail Bonding

Experience at Kinzua with a very poor track demonstrated the necessity of a rail bond to secure reliable electrical continuity throughout the rails constituting the block. Here, in 1872, Mr. Robinson conceived the invention of the bond wire as used today.

In an effort, however, to avoid the handicap of having to bore two holes in every rail of long sections of track, he equipped a signal section in 1873 with elastic steel plates bearing on the adjacent rails at the joints. This did not prove as satisfactory, however, as the bond wire. He therefore used bond wires made after his original conception, on every installation he made after 1873.

He made his bond wire in two forms. In the second form he made studs slightly tapering, bored holes through them, inserted the ends of the wire in these holes, brazed them together and drove these studs securely into holes bored in the adjacent rails. An examination of these bonds after several years' service showed that they were apparently in as good condition mechanically and electrically as when first put in place.

The Rail Bond is now an essential basic feature of practically every one of the electric railway systems now in operation, since they all use the track for a return, and the track rails must be securely bonded in order to insure indispensable electrical continuity of the circuit.

In addition to his signal system, therefore, Dr. Robinson is clearly entitled to the credit of having made, before the inception of electric railroading, a simple basic invention in his bond wire, which has made modern electric railroading possible, an invention indispensable to the successful operation of electric railroading as practiced today.

This invention has saved the electric roads untold millions of dollars and enabled them to accomplish results in a simple manner which could not otherwise be as well secured at any cost, by the only alternative method, of running return contact conductors in the air.