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

Fig. 13.

Fig. 14.

Fig. 15.

Fig. 16.

In Robinson's British patent No. 3479, of August 29, 1879, aforesaid, he illustrated the form of bond shown in Figs. 15 and 16, which is an equivalent of that shown in Fig. 14, used by him in 1876.

Mr. Robinson claimed the bond wire broadly in this British patent, in the following claims:

10. "The wire A³ in combination with the rails B³, B³, and securely fastened thereto, for the purpose described.