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

The batteries for operating the signals will last for months without attention, and one man can readily attend to all the signals and batteries throughout the whole extent of a road.

In all cases, where practicable, the signal wire should be carried through the coils of a bell-magnet in the nearest office. By this means the operator is informed when the battery power is decreasing, and warned that it requires renewing.

Office connections can be made, when desired, so that the signals may be operated by a telegraph key from the office, as well as by passing trains.

The signal wires may be tapped at intervals all along the line, and led into small cast iron boxes placed conveniently on the telegraph poles. Conductors of all trains, furnished with keys to these boxes, can, in case of special accident, go to the nearest box, touch a key within the same, and thus set danger signals at some distance in front and rear of their trains. The telegraph keys in these boxes not only set the danger signals as described, but they also place the said signals, for the time being, entirely out of control of moving trains.

THE CLOSED CIRCUIT.

The new system, as described, with closed circuit, is the best ever devised for "block-signaling," since the failure of the battery through neglect or otherwise, cannot possibly be productive of disastrous results to the train, however implicitly the signals may be relied on.

From the French of Feb. 1872 [Translation].

88th claim. "Connecting a battery B5, and a magnet M5 with the rails a9, b9, of a section of railroad track C5 in such a manner that when said rails are joined by a metallic bridge, the electric current will be diverted from the magnet M5, but so that when said bridging device is removed from said section C5 the electric current will be free to pass through and charge the magnet M5."

93d. "A signal or signals audible or visual in combination with the battery B5 and the rails of a railroad track, the whole being arranged to actuate the signal or signals, substantially as described."

William Robinson.