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Cyclopedia

Telephony and Telegraphy

TELEPHONY, SUBSTATIONS, PARTY LINE SYSTEMS, PROTECTION, MANUAL SWITCHBOARDS, AUTOMATIC SYSTEMS, POWER PLANTS, SPECIAL SERVICE FEATURES, CONSTRUCTION, ENGINEERING, OPERATION, MAINTENANCE, TELEGRAPHY, WIRELESS TELEGRAPHY AND TELEPHONY, ETC.

TELEPHONE AND TELEGRAPH EXPERTS, AND ELECTRICAL ENGINEERS OF THE HIGHEST PROFESSIONAL STANDING

FOUR VOLUMES

CHICAGO

AMERICAN SCHOOL OF CORRESPONDENCE

Entered at Stationers' Hall, London All Rights Reserved

Authors and Collaborators

KEMPSTER B. MILLER, M.E. Consulting Engineer and Telephone Expert Of the Firm of McMeen and Miller, Electrical Engineers and Patent Experts, Chicago American Institute of Electrical Engineers Western Society of Engineers

GEORGE W. PATTERSON, S.B., Ph.D. Head, Department of Electrical Engineering, University of Michigan

CHARLES THOM Chief of Quadruplex Department, Western Union Main Office, New York City

ROBERT ANDREWS MILLIKAN, Ph.D. Associate Professor of Physics, University of Chicago Member, Executive Council, American Physical Society

SAMUEL G. McMEEN Consulting Engineer and Telephone Expert Of the Firm of McMeen and Miller, Electrical Engineers and Patent Experts, Chicago American Institute of Electrical Engineers Western Society of Engineers

LAWRENCE K. SAGER, S.B., M.P.L. Patent Attorney and Electrical Expert Formerly Assistant Examiner, U.S. Patent Office

GLENN M. HOBBS, Ph.D. Secretary, American School of Correspondence Formerly Instructor in Physics, University of Chicago American Physical Society

CHARLES G. ASHLEY Electrical Engineer and Expert in Wireless Telegraphy and Telephony

FRANCIS B. CROCKER, E.M., Ph.D. Head, Department of Electrical Engineering, Columbia University Past-President, American Institute of Electrical Engineers

MORTON ARENDT, E.E. Instructor in Electrical Engineering, Columbia University, New York

EDWARD B. WAITE Head, Instruction Department, American School of Correspondence American Society of Mechanical Engineers Western Society of Engineers

DAVID P. MORETON, B.S., E.E. Associate Professor of Electrical Engineering, Armour Institute of Technology American Institute of Electrical Engineers

LEIGH S. KEITH, B.S. Managing Engineer with McMeen and Miller, Electrical Engineers and Patent Experts Chicago Associate Member, American Institute of Electrical Engineers

JESSIE M. SHEPHERD, A.B. Associate Editor, Textbook Department, American School of Correspondence

ERNEST L. WALLACE, B.S. Assistant Examiner, United States Patent Office, Washington, D. C.

J. P. SCHROETER Graduate, Munich Technical School Instructor in Electrical Engineering, American School of Correspondence

Authorities Consulted

The editors have freely consulted the standard technical literature of America and Europe in the preparation of these volumes. They desire to express their indebtedness particularly to the following eminent authorities, whose well-known works should be in the library of every telephone and telegraph engineer.

Grateful acknowledgment is here made also for the invaluable co-operation of the foremost engineering firms and manufacturers in making these volumes thoroughly representative of the very best and latest practice in the transmission of intelligence, also for the valuable drawings, data, suggestions, criticisms, and other courtesies.

Foreword

The present day development of the "talking wire" has annihilated both time and space, and has enabled men thousands of miles apart to get into almost instant communication. The user of the telephone and the telegraph forgets the tremendousness of the feat in the simplicity of its accomplishment; but the man who has made the feat possible knows that its very simplicity is due to the complexity of the principles and appliances involved; and he realizes his need of a practical, working understanding of each principle and its application. The Cyclopedia of Telephony and Telegraphy presents a comprehensive and authoritative treatment of the whole art of the electrical transmission of intelligence.

The communication engineer--if so he may be called--requires a knowledge both of the mechanism of his instruments and of the vagaries of the current that makes them talk. He requires as well a knowledge of plants and buildings, of office equipment, of poles and wires and conduits, of office system and time-saving methods, for the transmission of intelligence is a business as well as an art. And to each of these subjects, and to all others pertinent, the Cyclopedia gives proper space and treatment.

The sections on Telephony cover the installation, maintenance, and operation of all standard types of telephone systems; they present without prejudice the respective merits of manual and automatic exchanges; and they give special attention to the prevention and handling of operating "troubles." The sections on Telegraphy cover both commercial service and train dispatching. Practical methods of wireless communication--both by telephone and by telegraph--are thoroughly treated.

The drawings, diagrams, and photographs incorporated into the Cyclopedia have been prepared especially for this work; and their instructive value is as great as that of the text itself. They have been used to illustrate and illuminate the text, and not as a medium around which to build the text. Both drawings and diagrams have been simplified so far as is compatible with their correctness, with the result that they tell their own story and always in the same language.

The Cyclopedia is a compilation of many of the most valuable Instruction Papers of the American School of Correspondence, and the method adopted in its preparation is that which this School has developed and employed so successfully for many years. This method is not an experiment, but has stood the severest of all tests--that of practical use--which has demonstrated it to be the best yet devised for the education of the busy, practical man.

In conclusion, grateful acknowledgment is due to the staff of authors and collaborators, without whose hearty co-operation this work would have been impossible.

Table of Contents

VOLUME II

Common-Battery Switchboards--Line Signals--Cord Circuit--Lamps--Mechanical Signals--Relays--Jacks--Switchboard Assembly--Transfer Switchboard--Transfer Lines--Handling Transfers--Multiple Switchboard--Busy Test--Influence of Traffic--Magneto-Multiple Switchboard--Multiple Boards: Series, Branch-Terminal, Modern Magneto, Common-Battery--Western Electric No. 1 Relay Board--Western Electric No. 10 Board--Types of Multiple Boards--Apparatus--Trunking--Western Electric and Kellogg Trunk Circuits

Automatic vs. Manual--Operation--Selecting Switch--Line Switch--Trunking Systems--Two- and Three-Wire Systems--Subscriber's Station Apparatus--First and Second Selector Operation--Connector--Release after Conversation--Multi-Office System--Automatic Sub-Offices--Rotary Connector--Party Lines--Two-Wire Automatic System--Lorimer System--Central-Office Apparatus--Operation--Automanual System--Operation--Subscriber's Apparatus--Operator's Equipment--Switching Equipment--Distribution of Calls--Connection--Speed

Currents Employed--Types--Operator's Transmitter Supply--Ringing-Current Supply--Auxiliary Signaling Current--Primary Sources--Duplicate Apparatus--Storage Batteries--Power Switchboards--Circuits--Central-Office Building--Arrangement of Apparatus--Manual Offices--Automatic Offices

Private-Branch Exchanges--Switchboards--Supervision--With Automatic Offices--Battery Supply--Ringing Current--Inter-Communicating Systems--Magneto System--Common-Battery Systems--Types--Long-Distance Switching--Operator's Orders--Trunking--Way Stations--Traffic--Measured Service--Charging--Rates--Toll Service--Local Service

Phantom, Simplex, and Composite Circuits--Ringing--Railway Composite--Telephone Train Dispatching--Railroad Conditions--Transmitting Orders--Apparatus--Telephone Equipment--Types of Circuits--Test Boards--Blocking Sets--Dispatching on Electric Railways

REVIEW QUESTIONS Page 359

INDEX Page 373

THE SIMPLE COMMON-BATTERY SWITCHBOARD

Concentration of sources of energy into a single large unit, the simplification of the subscriber's station equipment, and the ready adaptability to automatic signaling from the subscriber to the central office are, therefore, the reasons for the existence of the common-battery system.

To say the least, the telephone transmission to be had from common-battery systems is no better than that to be had from local-battery systems, and as a rule, assuming equality in other respects, it is not as good. It is perhaps true, however, that under average conditions common-battery transmission is somewhat better, because whereas the local batteries at the subscribers' stations in the local-battery system are not likely to be in uniformly first-class condition, the battery in a common-battery system will be kept up to its full voltage except under the grossest neglect.

The places in which the magneto, or local-battery, system is to be preferred to the common-battery system, in the opinion of the writers, are to be found in the small rural communities where the lines have a rather great average length; where a good many subscribers are likely to be found on some of the lines; where the sources of electrical power available for charging storage batteries are likely either not to exist, or to be of a very uncertain nature; and where it is not commercially feasible to employ a high-grade class of attendants, or, in fact, any attendant at all other than the operator at the central office.

In large or medium-sized exchanges it is always possible to procure suitable current for charging the storage batteries required in common-battery systems, and it is frequently economical, on account of the considerable quantity of energy that is thus used, to establish a generating plant in connection with the central office for developing the necessary electrical energy. In very small rural places there are frequently no available sources of electrical energy, and the expense of establishing a power plant for the purpose cannot be justified. But even if there is an electric light or railway system in the small town, so that the problem of available current supply does not exist, the establishment of a common-battery system with its storage battery and the necessary charging machinery requires the daily attendance at the central office of some one to watch and care for this battery, and this, on account of the small gross revenue that may be derived from a small telephone system, often involves a serious financial burden.

Telephone operating companies who have changed over the equipment of old plants from magneto to common battery have sometimes been led into rather serious difficulty, owing to the fact that their lines, while serving tolerably well for magneto work, were found inadequate to meet the more exacting demands of common-battery work. Again in an old plant the change from magneto to common-battery equipment involves not only the change of switchboards, but also the change of subscribers' instruments that are otherwise good, and this consideration alone often, in our opinion, justifies the replacing of an old magneto board with a new magneto board, even if the exchange is of such size as to demand a small multiple board.

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