ELEMENTS

OF

RAILWAY SIGNALING

 

 

PAMPHLET 1979

June 1979

 

 

 

 

 

 

 

 

 

 

 

GENERAL RAILWAY SIGNAL

 A UNIT OF GENERAL SIGNAL

P.O. BOX 600

 

ROCHESTER NEW YORK 14602

 

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Main office and manufacturing facilities of the General Railway Signal Company at Rochester, New York.

 

 

 

 

 

 

A-3121                   Copyright General Signal Corporation 1954. 1979(c)                   Printed in U.S.A.

 

 

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Gerald E. Collins, President of General Railway Signal Company and Group Executive of General Signal.

 

 

 

 

 

ABOUT THIS BOOK

 

GRS has been supplying signal systems and equipment to railroads and to rail transit since 1904. This book is our way of celebrating our 75th anniversary, of saying, “Thank you”, to our many friends.

 

We offer it as a means to help those who are entering the signaling field. It is not a complete course in railway signaling but an introduction to this fascinating and complex subject. We think it will be useful as an over-all view of signaling systems, their principles of operation, and how these principles are applied.


TABLE OF CONTENTS

 

About This Book …………………………………………………………………             3

Brief History of Railway Signaling ………………………………………………            5

Track Circuits, Non-Coded ………………………………………………………        100

Block Signaling, Single-Direction Running ……………………………………..         201

Block Signaling, Double-Direction Running …………………………………….         301

Track Circuits, Coded and Electronic ……………………………………………         400

Block Signaling Adjuncts ………………………………………………………..         500

Cab Signals ………………………………………………………………………         601

Train Control …………………………………………………………………….         700

Highway Crossing Warning ……………………………………………………..         800

Relay Interlocking ……………………………………………………………….         900

Centralized Traffic Control ………………………………………………………      1000

Automatic Car Classification …………………………………………………….      1100

Rapid Transit Systems ……………………………………………………………      1201

Personal Rapid Transit Systems ………………………………………………….       1301

Industrial Railway Systems ………………………………………………………       1400

Power Supply …………………………………………………………………….       1501

GRS Offices ……………………………………………………………………...     Inside back cover

 

 

 

 

 

 

 

The information contained herein is intended as illustrative only and is furnished without assuming any obligations. The circuits are typical only - do not use for design or wiring purposes; the results may be inoperable or unsafe systems. The description and illustrations of circuits, systems and devices herein do not convey to the purchaser of any such devices a license to such circuits and systems that may be covered by the patents of the General Signal Corporation or others.


A BRIEF HISTORY OF RAILWAY SIGNALING

 

 

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INTRODUCTION

 

Although the date of 1814 is given as the first practical use of George Stephenson’s invention, the steam locomotive, signaling is even older. The first rail cars were pulled by horses or mules and were used in mines and quarries. Records as early as 1806 show that hand and arm signals were used to direct the drivers of these early trains”. Hand signals, flags - and at night, lanterns - were used to signal B & 0 trains in 1829. In some instances, a mounted flagman preceded the train - indeed this custom continued in New York City, on West St., as late as the twenties.

 

 

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A mounted flagman once warned of an approaching train.

 

Signaling using fixed wayside signals probably first began, in the United States, on the New Castle and Frenchtown R.R., in 1832. This 17-mile long railroad, connecting New Castle, Delaware with French- town, Maryland, used fixed signals, flags at first and later ball signals, to pass information from one terminal to another.

 

 

BLOCK SIGNALING

 

In the early days of railroading, trains were operated (more or less) by schedules. Thus train separation was a time separation. As traffic increased, tracks were divided into blocks, and train separation was by space interval. Thus block signaling began. Various electrical and mechanical systems were tried. Basically, they were designed to let one train pass into a block and to inhibit the block entering signal from clearing to allow another train into the block until the first train was reported to have left the block. Later systems added a permissive feature, allowing trains to follow each other into the same block.

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Ball signals like this one were observed through telescopes from distant block offices.

 

Beginning in 1851, the electric telegraph was used to determine the locations and progress of trains along the line and to transmit train orders to expedite traffic.

 

These systems all required substantial manpower and had no protection against a part of a train being accidentally left in a block between signal stations.

 

August 20, 1872, marked one of the most important events in railway signaling, the invention of the closed track circuit by Dr. William Robinson. First installed at Kinzua, Pa. on the Philadelphia and Erie R.R., the closed track circuit soon proved its worth, and other installations followed rapidly. All modern track circuits are based on Dr. Robinson’s original concept, even though their capabilities have been greatly amplified by modern track relays, coding, and more recently, electronic techniques such as the GRS high-frequency jointless track circuits.

 

The next great advance in the block signaling area of railway signaling came in 1911, when a GRS engineer, Sedgwick N. Wight, invented absolute permissive block signaling. This system, now called APB, allows trains to operate in either direction on single track with full signal protection for both following and opposing movements. A later GRS development, Trakode, provides APB signaling without the use of signal-control line wires.

 

 

INTERLOCKING

 

The first installation resembling interlocking was installed in England, in 1843, at a place called Bricklayer’s Arms Junction. The switches and signals were operated by a switchman. Connections to the field were via pipe and wire pull. There were hand levers to operate the switches and foot stirrups to work the signals. There was no interlocking among the switches and signals. Switches were sometimes thrown under trains and signals cleared over open switches, but the advantages of centralizing control were achieved.

 

Various arrangements were soon devised to prevent the operation of occupied switches and then to interlock the switch and signal controls. However, it wasn’t until 1856 that the first mechanical interlocking appeared that met what we now consider essential interlocking requirements. It was developed in England by John Saxby.

 

The first interlocking in the United States, a Saxby & Farmer imported from England, was put in service in 1870, at Trenton, N.J., on the property of the United New Jersey Canal and Railroad Companies. Many more mechanical interlockings were installed, and numerous

 

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A meet on the world’s first installation of absolute permissive block signaling, 1911, on the Toronto, Hamilton & Buffalo Ry.

 

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Early signaling required muscle power. This is the interior of the A.B. signal box on the South-Eastern Ry., London Bridge Station, in 1866.

 

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In 1904, this GRS electric interlocker was installed at East Norwood, Ohio, on the B&O Southwestern RR to replace the original Taylor machine.

 

improvements were made to the system. American manufacturers, GRS among them, produced the bulk of mechanical interlockings in the U.S. until they were gradually superseded by various types of power interlockings, interlockings which did not depend on human muscle power to throw the switches and set the signals.

 

Several power interlocking arrangements were tried, such as hydropneumatic and electro-pneumatic systems, which proved the advantages of power operation but suffered from various disadvantages. Then, in 1901, the Taylor Signal Co., one of the predecessors of GRS, put in service the first all-electric, dynamic indication interlocking, at Eau Claire, Wis., on the Chicago, St. Paul, Minneapolis and Omaha Railway. This system was unique in that it proved the operations of the switches and signals by requiring reception of a “dynamic indication” current back at the control tower to operate the locking latches in the levers. The dynamic indication current was generated by the free spin of the armature in the electric motor in the semaphore signal and in the electric switch machine as they completed their movement to a called-for position. This system was an immediate success, and thousands of levers were installed, some of which are still in service.

 

The next development, relay interlocking, which requires no mechanical locking between the levers, developed with centralized traffic control.

 

 

CENTRALIZED TRAFFIC CONTROL

 

On July 25, 1927, the first centralized traffic control system in the world went in service between Stanley and Berwick, Ohio, on the Ohio Division of the New York Central Railroad. This system, invented by the same Sedgwick N. Wight of the General Railway Signal Company who had earlier invented APB, was a tremendous stride forward in improving facility and economy of train operation.

 

Here is a first-hand account of operation with the new system as given in an address by Mr. J. J. Brink- worth of the New York Central Railroad before the Signal Section of the Association of American Railroads in 1947. I was particularly involved in centralized traffic control in 1927 I went to Rochester, to the General Railway Signal Company plant, and saw the actual machine there. I, of course, became acquainted with Mr. S. N. Wight of that Company, who studied out the details of the cTc machine. I went to his house and in the back room we talked it over in detail for hours.

 

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The world’s first centralized traffic control, from Stanley to Berwick, Ohio, on the New York Central, was controlled from this machine at Fostoria, Ohio.

 

“Then we came to 1927, when the final date was set to install centralized traffic control on the Toledo & Ohio Central and put it into service. Needless to say, we were all over at Fostoria, Ohio, and we watched the progress of the various signals being put in along the approximately 40 miles of railroad between Toledo and Berwick. Then, after a comparatively short time, trains started to move over that piece of single track for the first time without train orders.

 

“I recall very distinctly, as we had supper in the hotel at Fostoria and got through, I said to the gang, I do not know what you fellows are going to do tonight, but I’m going over to the tower at Fostoria and stay

there until I see a non-stop meet. Well, they all decided that if the boss was going over, the rest of the gang had better go, too. So we went over to the tower at Fostoria in the evening. The dispatcher was there and he was just filled up with enthusiasm on this new gadget called centralized traffic control.  Along about 10:00 o’clock, he just yelled right out loud, “Here comes a non-stop meet”. Well, we all gathered around the machine and watched the lights that you know all about, watched the lights come towards each other and pass each other without stopping.

 

“That, to me, and to you, too, was history on American railroads, the first non-stop meet on single track without train orders, of course, that we knew of. We waited at Fostoria until the southbound train arrived there and you never saw such enthusiasm in your life as was in the minds and hearts of that crew, the first non-stop meet of which they had ever heard.”

 

Thus occurred the first non-stop meet, today commonplace on thousands of miles of cTc.

 

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The beginnings of pushbutton signal systems, this NX interlocking machine (the world’s first) was placed in service at Brunswick, England in 1937,

 

 

ALL-RELAY INTERLOCKING

 

All-relay interlocking was an outgrowth of the principles applied so successfully in centralized traffic control. Now the cumbersome lever locking beds of the electric interlocking machine were abandoned in favor of relay interlocking between the switches and signals in the field. Control distance ceased to be an important factor.

 

GRS furnished equipment for the first remotely controlled, unit-wire all-relay interlocking system, put in service February 1929, on the Chicago, Burlington and Quincy at Lincoln, Nebraska.

 

The first installation of an all-relay interlocking with pushbutton automatic selection of routes and positioning of switches and signal’s, the GRS Type NX, was made at Brunswick, England, on the Cheshire Lines, in February of l93. The first NX route-type interlocking in the United States was installed at Girard Jct., Ohio, on the New York Central in 1937.

 

 

AUTOMATIC TRAIN CONTROL

 

It is doubtful if any special subject ever received as much attention as did automatic train control. Thousands of patents were issued, millions of dollars spent in experimentation, and yet only a few systems have survived the tests of practical use.

 

A trial installation of GRS intermittent inductive train stop was made on the Buffalo. Rochester and Pittsburgh Railway in 1919. By 1923, the first commercial installation was made on the Chicago and North Western Railway, and many installations followed.

 

Today, however, the most modern types of train control are used on rapid transit systems, such as the GRS installations at Washington, D.C., Boston, Chicago, and, most recently, Atlanta.

 

 

CAR CLASSIFICATION

 

GRS led the field with the first commercial installation of all-electric car retarders, in 1926, at East St. Louis on the Illinois Central Railroad.

 

The next significant development in car classification was the invention by GRS, in 1950, of the automatic switching system. The initial installations of this system were made at Markham Yard, Illinois, on the Illinois Central Railroad, and St. Luc Yard, Montreal, on the Canadian Pacific, both in 1950.

 

In 1953, another GRS invention, automatic retarder control using a GRS analog computer was installed at Kirk Yard, Gary, Indiana, on the Elgin, Joliet & Eastern. This system marked the use, now common, of radar and of computer technology in railway signaling.