Transcriber's Note: Minor typographical errors have been corrected without note. Irregularities and inconsistencies in the text have been retained as printed. Words printed in italics are marked with underscores: _italics_. Words printed in bold are marked with tildes: ~bold~. A caret (^) is used to indicate that the following character is printed as a superscript. [Illustration: Photograph and written signature of William Robinson] 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 SIGNAL SECTION AMERICAN RAILWAY ASSOCIATION NEW YORK 1922 PREFACE Believing that no more fitting memorial can be prepared in honor of Dr. William Robinson than to reproduce the salient points relating to his great achievement as written and published by himself in 1906 under the title of "History of Automatic Electric and Electrically Controlled Fluid Pressure Signal Systems for Railroads," the committee has accordingly drawn largely from this pamphlet for the material contained in Part I. Part II is devoted to W. A. Baldwin, formerly General Superintendent of the Pennsylvania Railroad, who was responsible for the first installations of automatic block signals controlled by track circuits. As this memorial would not be complete without a description of the track circuit, its principle and operation under present day signaling practices, Part III is accordingly devoted to this subject. HERBERT S. BALLIET, _Chairman_; KEITH E. KELLENBERGER, HENRY M. SPERRY, _Committee_. CONTENTS RESOLUTION 1 I THE INVENTION OF THE TRACK CIRCUIT 3 Robinson's Patent 42 Robinson's Description of His Invention 50 Dr. Robinson's Record, Wesleyan University 59 Dr. Robinson's Record, A.I.E.E. 60 II WILLIAM A. BALDWIN 68 III THE TRACK CIRCUIT 76 Its Principle 77 Its Characteristics 85 The Extent of its Use 98 IV THE TRACK CIRCUIT IN GREAT BRITAIN AND ON THE CONTINENT, BY T. S. LASCELLES 103 Some of the First Installations 106 Track Circuits on the Continent 109 THE TRACK CIRCUIT[1]