communication-past and present

Communication-Past and PresentBy Bancroft Gherardi, President A.I.E.E. 1927-28

WAfHEN in May 1884 Pointing out that when the A.I.E.E. was only 8 years. Radio-teleg-a group of men, founded in 1884 telegraphy was 40 years raphy and radio-teleph-numbering perhaps ony did not exist. From

a hundredth of our present old and telephony 8 years old, the author the first, a realization ofmembership, gathered to- traces briefly the significant developments the advantages to be de-gether to found the Ameri- and tremendous growth of electrical com- rived from electrical com-can Institute of Electrical munication and the signifcance and im- munication led to the rapidEngineers, none of them unctoanthsiifacendi- development of both teleg-could foresee what the or- portance of the parallel growth of the Insti- raphy and telephony. Howganization itself would grow tute. "Both grew out of the extension of much of this has takento be or the future of the our knowledge of certain laws of nature, place during the 50 yearsindustries which would be of the life of the Americanfounded on electrical knowl- and both were encouraged in their growth by Institute of Electrical Engi-edge. They were inter- the social and economic results that were neers is briefly indicated byested in the theory and the possible from the application of elec- the following figures. Dur-practical use of electricity. tricity." The record of 50 years of coming 1884, there were sentThey must have believed y y about 40 million telegraphthat something well worth munication development is traced through messages in the Unitedwhile would grow out of the a half century of Institute publications. States. In 1929, the peakapplication of electricity to year, just prior to the de-the service of mankind, but pression, this figure had in-the tremendous develop- creased to 235 million mes-ments that would result from applying sages. In 1884, there were 198 millionelectricity to social and economic pur- telephone messages sent in the Unitedposes were concealed then in the dark- States, and in the peak year 1930 theness of the future. I feel honored in usage of the telephone had reached thebeing asked to perform the pleasant stupendous total of 27,800 millionduty of recording at this time, when messages. For several recent yearsthe Institute is completing the first the messages sent electrically have50 years of its life, what has happened greatly exceeded in number the totalin the communication art during that of the first-class mail pieces in theperiod. United States.From the earliest days until the in- It is not a mere coincidence that the

vention of the telegraph, communica- life of the American Institute of Elec-tion between persons at a distance was trical Engineers has been paralleled byessentially a matter of transportation. the tremendous growth of electricalEither a written message was transported by some communication. Both grew out of the extension ofone of the means then available or the messenger our knowledge of certain laws of nature, and bothhimself traveled, either on foot, on horseback, by were encouraged in their growth by the social andstage coach, by boat, or by railroad. With some economic results that were possible from the applica-negligible exceptions used only for specialized pur- tion of electricity.poses, communication was dependent upon trans- The early development of the telegraph was closelyportation and subject to all its limitations. With associated with the railroads which had an urgentthe invention and development of the electric tele- need for this form of communication, and telegraphgraph, communication by the written message first lines were very generally built along the railroadbecame independent of transportation. In the routes. The wires were generally of iron; hardUnited States the first application was by Morse in drawn copper was not invented until 1877, and cable1844. Still, however, communication by the spoken development did not start until about the beginningword could not be carried on over distances of more of our 50-year period. Many of the present formsthan a few hundred feet and conveniently only over of telegraph circuit had been worked out, includingdistances of a few feet. Alexander Graham Bell in duplex and quadruplex and Baudot's multiplex and1876, by the invention of the telephone, offered the printing telegraph, although this form was not ap-possibility of communication by the spoken word plied in this country until a later date. Harmonicbetween people separated by considerable distances, telegraphs which foreshadowed our modern carrierso that it was no longer necessary for those desiring telegraph developments had been worked upon bysuch communication to meet at a common point to inventors, including Alexander Graham Bell, for amake conversation possible. decade or more, and Gray's harmonic telegraph hadWhen the Institute was founded, telegraphy was been given a trial. Following the first temporary

40 years old. The telephone had been invented success in 1858, permanent transatlantic telegraph

MAY 1934 50th ANNIVERSARY NUMBER 745

service by cable was established in 1866. One of largely come about through the development ofmy valued possessions is a medal presented by the successful carrier telegraph systems, realizing at lastNew York Chamber of Commerce to my father for the dream of the early telegraph workers that ahis part in the early cable laying expedition, as an large number of telegraph circuits could be providedofficer of the U.S. Frigate Niagara. on one pair of wires.3855 An important requirement

Fire alarm and burglar alarm systems were well for the success of this development was the applica-developed and police alarm systems were just coming tion of electrical means for separating the channels,into general use. Stock quotation systems had been whereas the early inventors necessarily tried to useestablished. Railway signaling systems had been mechanical means.5 The carrier telegraph art alsoinvented, but only one railroad in the United States depends upon the vacuum tube, itself a developmentwas equipped throughout its entire length with auto- of the last 20 years. 1 5matic electric block signals. An editonral in the Many advances were made in the operation ofSeptember 1884 issue of the "Electrician and Elec- long submarine telegraph cables through loading andtrical Engineer" refers to the adoption of automatic other improvements by means of which the messagesignals as the most important step to be taken in the capacity of these cables was increased severaldirection of perfecting our modern railway systems. fold.56'85

In 1884 telephony was still very young. There A striking technical development of this period ishad been sufficient technical development to pro- radio, first applied to telegraphy. Although iso-duce the fundamentals of a telephone exchange lated experiments, which were early experiments insystem in early crude form. Early types of the radiation, date back to 1842 with Joseph Henry'scarbon transmitter had been invented and placed in detection of Leyden jar disturbances at distancesservice. The first switchboards had been con- of several hundred feet and lightning discharges atstructed, and the first multiple board was placed in distances of 20 miles and while in 1864 Maxwellservice in Chicago in 1879. The use of the metallic advanced his electromagnetic theory which showedcircuit telephone system had just begun. A begin- radio communication to be possible, the birth ofning had been made in the development of telephone radio science is generally associated with Hertz'wires in cable and, as already noted, hard drawn brilliant work in 1887 and the beginning of practicalcopper had just been invented. Long distance application came with the work of Marconi intelephony was beginning, a line from Boston to 1896.6,9,1 From then the development of radio-Providence having been established in 1881. The telegraphy was rapid, transatlantic service beingfirst conversation between New York and Boston established in 1908 and ships being generallyusing hard drawn copper circuits took place in equipped with this valuable means of promoting1884, the year of the founding of the Institute. safety by the year 1913.19,30,34,93

It is difficult within the scope of a brief statement Although in 1884 that then novel and primitiveto indicate adequately the extraordinary develop- device, the telephone, had already been put to work,ment of the technique of electrical communication there being about 150,000 in use in the Unitedthat has taken place during the past 50 years, States, the technical development of telephonebuilding upon the fundamental technical principles systems had only started. This development hasthat had been established by 1884 and applying included 3 major groups of problems: (1) apparatusmany new technical principles discovered since. at each telephone station to convert sound energyThe hand sending method of operating telegraph into electrical waves and back again and to provide

circuits has been largely displaced by the applica- signals to attract the attention of users; (2) switch-tion of the printing telegraph. Although the idea ing systems at central points for rapidly and accu-of having telegraph impulses print the message is as rately connecting together any 2 telephones thatold as telegraphy itself, the present successful forms might desire to communicate with each other; andof apparatus are of modern development represent- (3) means for transmitting the telephonic currentsing the culmination of many decades of intensive over distances little or great without excessive losseffort and the creation of successively better forms or other modification.of this apparatus'0 (references are by number to Shortly after the Institute was founded came theitems in bibliography). The types now in general first successful granular carbon telephone trans-use were all developed within the last 20 years.36' 41 mitter, so great an improvement over the earlierThe scope of practical application of printing tele- forms of transmitter that, by many modificationsgraph apparatus has been extended by a new and improvements, it has become, without changingmethod for maintaining synchronism or more exactly its essential principle, the highly developed telephoneisochronism between the machines on the same transmitter of today. At about the same time camecircuit by the so-called start-stop principle which is Carty's invention of the bridging principle to replaceutilized in most of the printing telegraph machines for telephone circuits the series types of connectionnowvin operation.4' inherited from the telegraph practice.'2 One of its

Telegraph circuits, where not in cable, are now many useful applications was to the signal bells atlargely built of hard drawn copper, only about 10 telephone stations, resulting in a great improvementper cent of the telegraph circuit mileage still making in performance. The hand set type of arrangement,use of iron. There has been a great extension in the while suggested early in this epoch and used in ause of telegraph circuits in cable, a third of the limited way, presented serious technical difficultiestelegraph circuit mileage of the country now being which, for the severe requirements for service in theof that type. This use of telegraph in cables has United States, were overcome only in recent years.89

746 50th ANNIVERSARY NUMBER ELECTRICAL ENGINEERING

Telephone switchboards of the early forms were circuit in the telephone plant today. Now, throughrelatively crude. In the period 1886-1894, the com- a further series of technical developments, we facemon battery switchboard was invented and intro- the prospect of having in the future carrier telephoneduced into practical use. Through successive methods applied to the toll cable plant giving a stillimprovements, the capacity of the common-battery more effective use of the pairs in telephone tollswitchboard was raised from a few hundred lines in cables.96the early models to 9,000 lines by the year 1902.12 In 1921 the telephone network, which theretoforeThroughout the development of switching systems had been confined to the continental area of thethere was a trend toward the greater use of auto- United States and Canada, began to stretch out tomatic devices, culminating in the development of the other countries. The first step was the establish-machine switching systems in which, for certain types ment of service between the United States andof calls, the switching is entirely mechanical. The Cuba through the placing of submarine telephonefirst successful step-by-step machine switching sys- cables of novel design.89 In 1915 the first experi-tem was placed in service in 1892. The panel ma- mental transatlantic telephone communications usingchine switching system designed to meet the com- radiotelephone links were held, and in 1927 commer-plex conditions of metropolitan areas was first cial transatlantic service was established. 33"44'69'80placed in service in 1915. Today dial system This form of development has expanded so rapidlyswitching has been provided for 40 per cent of the that today there are a quarter-million miles of inter-telephones of the country. 18,2126,27,35,4373383 continental radiotelephone circuits in service in theThe transmission of telephone currents over long world, and it is possible from any telephone in the

distances has been almost wholly a development of United States to reach 92 per cent of all the tele-this era. The first New York-Boston telephone phones in the world, located in 54 different countriescircuit in 1884 using hard drawn copper led to the on all the continents of the globe. In the last fewuse of copper for other interurban lines and the years telephone service has been extended to shipsdevelopment of the first transposition system to at sea by the use of radio, 19 ships being equippedprevent interference between numbers of telephone at the present time for connection to the Americancircuits carried on the same pole lines.4"331 Phan- telephone system.79 By the application of newlytom circuits to give 3 independent circuits on 2 developed materials and an advanced technique, itpairs of wires were experimented on in 1884, but will be possible to build a transatlantic telephonewere not successful until about 1902. In 1899 came cable when the continued increase in messages to bePupin's invention of loading, by which means the handled makes this desirable.transmission efficiency of telephone wires was in- With the rapid development of telephone net-creased. Loading not only permitted the extension works throughout the country, their use for theof open-wire circuits to greater distances, but it also transmission of music and for other entertainmentmade possible long distance telephone transmission purposes has been in the minds of the experts. Inover cable circuits.8'24'60 From small beginnings in the early days, however, such transmissions, while1902, when 49 pairs of a 10-mile cable from New interesting scientific demonstrations and well re-York to Newark were loaded for commercial service, ceived, did not represent a reproduction of music orthe use of this invention has extended until at the even of voices which was technically faithful. Withpresent time there are about 8,500,000 coils in use in the perfection of the telephone art it became possiblethe United States. Cables for phantom circuit to carry out such transmission with increasingly goodworking were made successful in 1910. reproduction. and beginning with about 1915 thereAnother great technical step in making possible the was a large development of such service using loud

extension of long distance telephony was the develop- speakers to bring the programs to audiences.47'49'53'70ment of the telephone repeater. The first commer- The latest step in perfecting the electrical trans-cial application of repeaters was in 1904 between mission of music, in which the transmission is notNew York and Chicago. These were of the mechani- only of extreme fidelity but includes the effects ofcal type, the vacuum tube repeater being first used acoustic perspective and also a range of volumes farcommercially in 1913.32 The combined effect of beyond that which can be produced directly by anthese advances in the art led to the opening of trans- orchestra, has just recently been described andcontinental service in 1915 and the rapid extension demonstrated before this Institute.97of the service toward the ideal of a universal service Improvements in radiotelephony led to the intro-between all points of the country.64'78 These de- duction, in 1920, of radio broadcasting of programs.velopments made possible the use of extensive long This has grown to its present large proportions withdistance telephone cable systems, including circuits about 600 radio transmitting stations broadcastingin cable 2,000 miles or more in length. In this way programs to 16 million radio receiving sets in thisit was possible to connect together, by means of country.48'4953"8'62'66'70 Many of these transmittingstorm-proof plant, many of the larger cities in the stations are linked together in groups by program

country.40'46'64transmission wire networks, aggregating about 35,000Carrier telephone systems, by which several inde- miles of circuit.77

pendent telephone channels are simultaneously car- The application of the technique developed fornied on one pair of open wires, marked another step electrical communication has led naturally to itsin long distance transmission. They were first ap- extension to uses other than those contemplated inplied commercially in 1918 between Baltimore and the original telephone and telegraph systems.5 37Pittsburgh.38'68'76 There are 575,000 miles of carrier Private wire telegraph systems have developed a


wide variety of uses, including automatic stock Institute paper should be on a subject of suchquotation boards and the transmission of weather fundamental importance, one on which a largemaps for air navigation.86 90 The last few years have number of the outstanding developments of electricalwitnessed the extension of application of electrical communication of the past 20 years depend andcommunication to assist the law enforcing agencies, which today is engaging to an increasing extent theincluding teletypewriter systems between the police attention of men in the electrical power field as welloffices and radiotelephone for continuous contact as in the field of electrical communication.with police automobiles.86 Radio communication As a result of the extension of the electrical trans-has been adapted extensively to the assistance of mission of the spoken and the written word, in thenavigation, both of ships and of aircraft, through United States today, where many of the fundamentalthe development of methods for direction finding, concepts originated and much of the technicalradio beacons, and similar purposes.74'75'81'90'95 There development was done, it is no exaggeration to sayhas been a rapid extension of remote control and that we can have almost instantaneous communica-of the transmission of information for a great variety tion between any 2 parts of our country. Whileof uses, the remote control of switches in power these developments have been most extensivelysystems and remote indications of switch positions applied in the United States, a somewhat similarand of loads and remote indications of water statement may be made as to the scope of electricallevels.91,92 communication in other industrial countries. InA recent, and in one sense ambitious, development addition, extending between the various nations

of electrical communication is television. The eye there is a well developed electrical communicationconveys much more information to the observer than system.the ear, receiving electromagnetic impulses very Communication is today an integral part of ourmuch more complicated in structure than the social and economic life. That the American Insti-acoustic impulses received in hearing. This is illus- tute of Electrical Engineers has contributed in atrated by the fact that in the electrical transmission substantial way to the accomplishment of theseof photographs over telephone circuits from 5 to results cannot be doubted. Among the leaders in15 minutes is required for the transmission of a that organization from time to time have been:photograph, whereas television is equivalent to Alexander Graham Bell, Michael I. Pupin, John J.transmitting at least 16 photographs per second. Carty, Norvin Green, Frank B. Jewett, and HarryThe very large number of electromagnetic impulses P. Charlesworth, each of whom served as its Presi-that must be transmitted in a second, or to express dent. These same men likewise have been leadersit another way, the wide band of frequencies required in the communication development of which we arefor the transmission of television signals, raises speaking. They are but a few of the thousandsdifficult problems both in the design of the terminal connected with the communication industry whoequipment and with reference to the transmitting have been members of the American Institute ofmedium, whether wire or radio. Successful demon- Electrical Engineers. Through its proceedings andstrations of television over a distance of 250 miles through the informal contacts with others madewere made in 1927, and technical development, possible by its meetings, all of these men havehoping for ultimate commercial application, is derived some of the knowledge and some of theactively continuing.65 inspiration necessary for the successful accomplish-The records of the Institute's proceedings are a ment of the communication enterprises, built up as

valuable library of these tremendous technical ad- they are upon complicated technical working.vances of the past 50 years. This is illustrated by As the fiftieth year of the life of our Institute drawsan appended bibliography of selected references from near to its end, we look back with satisfaction uponthe Institute publications in which are set forth the results of the application of electricity to thetechnical discussions of these important develop- welfare of mankind. We surely are warranted inments and to which reference has been made through- believing that if we could look forward into theout this review. Although no general discussion of years to come we would there see still other andthese papers is possible within the limits of this equally extraordinary developments, perhaps morearticle, it is of interest to note in passing the first extraordinary developments, which still lie beforepaper in the Institute's TRANSACTIONS. This was us and which will minister to the comfort and con-presented at the first technical meeting in October venience of the people of the United States and of1884, by Professor Houston and was entitled "Notes the world. In these developments the members ofon Phenomena in Incandescent Lamps." It dis- of the American Institute of Electrical Engineers,cusses the "Edison effect," that is, the discovery present and future, will play a distinguished part.that in an evacuated bulb an electnc current wouldflow in one direction between a hot filament andcold cathode, but not in the other direction. This Bibl.all will now recognize as the first 2-element vacuum glioraphy of Selected Communicationtube and the basis of the modern science of elec- References From Institute Publicationstronics which was stimulated 20 years later byDe Forest's addition of a third element and the 1. NOTE:S ON PHEINOMENA IN INCANDESCENT LAMPS, Edwin J. Houston.development by many workers of the great possi- 2. SYNCHXRONISM, Edwin 3. Houston. v. 1, 1884.bilities which such a 3-element tube possesses. It

ined ineetn an significant RECENT IMPROVEMENTS IN APPARATUS POR OCEAN CABLING, Charles

is, ined neetn nlsgaathtat the first Cuttriss. v. 5, 1888.


4. INDUCTIVE DISTURBANCES IN TELEPHONE CIRCUITS, J. J. Carty. v. 8, 49. HIGH QUALITY TRANSMISSION AND REPRODUCTION OF SPEECH AND MUSIC,1891. W. H. Martin and H. Fletcher. v. 43, 1924.

5. PRACTICAL ASPECTS OF Low FREQUENCY ELECTRICAL RESONANCE, M. I. 50. MEASURING METHODS FOR MAINTAINING THE TRANSMISSION EFFICIENCYPupin. v. 10, 1893. OF TELEPHONE CIRCUITS, F. H. Best. v. 43, 1924.

6. EXHIBITION OF MARCONI WIRELESS TELEGRAPH APPARATUS. v. 14, 1897. 51. PRACTICES IN TELEPHONE TRANSMISSION MAINTENANCE WORK, W. H.Harden. v. 43, 1924.7. HISTORICAL SKETCH OF THE FIRE ALARM TELEGRAPH, Adam Bosch. v. 14,

1897. 52. TRANSMISSION UNIT AND TELEPHONE TRANSMISSION REFERENCE SYSTEMS,8. PROPAGATION OF LONG ELECTRICAL WAVES, M. I. Pupin. v. 16, 1899. W. H. Martin. v. 43, 1924.

53. THE FUNCTION AND DESIGN OP HORNS FOR LOUD SPEAKERS, C. R. Hanna9. THE POSSIBILITIES OP WIRELESS TELEGRAPHY-A TOPICAL DISCUSSION, and J. Slepian. v. 43, 1924.v. 16, 1899.

54. ECHO SUPPRESSORS FOR LONG TELEPHONE CIRCUITS, A. B. Clark and10. A NEW PAGE PRINTING TELEGRAPH, William B. Vansize. v. 18, 1901. R. C. Mathes. v. 44, 1925.

11. SPEECHES AT INSTITUTE DINNER IN HONOR OF GUGLIELMO MARCONI, 55. VOICE-FREQUENCY CARRIER TELEGRAPH SYSTEM FOR CABLES, B. P.v. 19, 1902. Hamilton, N. Nyquist, M. B. Long, and W. A. Phelps. v. 44, 1925.

12. THE EVOLUTION OF THE TELEPHONE SWITCHBOARD, Thomas D. Lock- 56. THE LOADED SUBMARINE TELEGRAPH CABLE, Oliver E. Buckley. v. 44,wood. v. 21, 1903. 1925.

13. TRANSPOSITION AND RELATIVE LOCATION OF POWER AND TELEPHONE 57. METALLIC POLAR-DUPLEX TELEGRAPH SYSTEM FOR LONG SMALL-GAUGEWIRES, P. W. Lincoln. v. 21, 1903. CABLES, J. H. Bell, R. B. Shanck, and D. E. Branson. v. 44, 1925.

14. THE TELAUTOGRAPH, James Dixon. v. 23, 1904. 58. NOTES ON THE DEVELOPMENT OF A NEW TYPE OP HORNLESS LOUD SPEAKER,15. THE AUDION, Lee De Forest. v. 25, 1906. Chester W. Rice and Edward W. Kellogg. v. 44, 1925.

16. TRACK-CIRCUIT SIGNALING ON ELECTRIFIED ROADS, L. Frederick Howard. 59. DESIGN OF NON-DISTORTING POWER AMPLIFIERS, E. W. Kellogg. v. 44,

v. 26, 1907. 1925.

17. WIRELESS TELEPHONY, R. A. Fessenden. v. 27, 1908. 60. DEVELOPMENT AND APPLICATION OF LOADING FOR TELEPHONE CIRCUITS,

18. A STUDY OF MULTI-OFFICE AUTOMATIC SWITCHBOARD TELEPHONE SYS- Thomas Shaw and William Fondiller. v. 45, 1926.TEMS, W. Lee Campbell. v. 27, 1908. 61. METHODS OF HIGH QUALITY RECORDING AND REPRODUCTION OF MUSIC

19. ALTERNATOR FOR ONE HUNDRED THOUSAND CYCLES, E. F. W. Alexander- AND SPEECH BASED ON TELEPHONE RESEARCH, J. P. Maxfield and H. C. Harri-son. v. 28, 1909. son. v. 45, 1926.

20. THE MODERN TELEPHONE CABLE, Frank B. Jewett. v. 28, 1909. 62. RADIO BROADCAST COVERAGE OF CITY AREAS, Lloyd Espenchied. v. 45,1926.

21. A MODERN AUTOMATIC TELEPHONE APPARATUS, W. Lee Campbell. v. 29, 63. REPRACTION OP SHORT RADIO WAVES, William G. Baker and Chester W.1910.

Rice. v. 45, 1926.

22. AMERICAN TELEGRAPH ENGINEERING-NOTES ON HISTORY AND PRACTICE, 64. TRANSMISSION FEATURES oP TRANSCONTINENTAL TELEPHONY, H. H.William Maver, Jr., and Donald McNicol. v. 29, 1910. Nance and O B Jacobs. v. 45, 1926.23. TELEGRAPH TRANSMISSION, Frank F. Fowle. v. 30, 1911. 65. SYMPOSIUM ON TELEVISION. v. 46, 1927.24. THE COMMERCIAL LOADING OF TELEPHONE CIRCUITS IN THE BELL SYSTEM, 66. QUANTITATIVE DETERMINATION OP RADIo RECEIVER PERPORMANCE,Bancroft Gherardi. v. 30, 1911. H. D. Oakley. v. 46, 1927.25. SOME RECENT DEVELOPMENTS IN RAILWAY TELEPHONY, Gregory Brown.v.30S191R1o 67. A NEW ELECTRONIC RECTIFIER, L. 0. Grondahl and P. H. Geiger. v. 46,V. 30, 1911.

1927.26. THE SEmi-AUTOMATIC METHOD OP HANDLING TELEPHONE TRAPPIC, 68. CARRIER SYSTEMS ON LONG DISTANCE TELEPHONE LINES, H. A. Affel,Edward E. Clement. v. 30, 1911......................... C. S. Demarest, and C. W. Green. v. 47, 1928.27. AUTOMATIC PRIVATE BRANCH EXCHANGE DEVELOPMENT IN SAN FRAN-27.AUTOMATIC PRIVATE BRANCH EXCHANGE DEVELOPMENT IN SAN FEaN- 69. TRANSATLANTIC TELEPHONE SERVICE, K. W. Water-son and 0. B. Black-Cisco, Gerald Deakin. v. 31, 1912. well. v. 47 (J.), 1928.28. REPORT BY THE JOINT COMMITTEE ON INDUCTIVE INTERFERENCES TO THE 70 LOUDSPEAKERS OP HIGH EPPICIENCY AND LOAD CAPACITY, c. R. Hanna.RAILROAD COMMISSION OF THE STATE OF CALIFORNIA. v. 33, 1914. V. 47, 1928.29. RECENT RESULTS OBTAINED FROM THE PRESERVATIvE TREATMENT OF 71. CERTAIN Topics IN TELEGRAPH TRANSMISSION THEORY, H. Nyquist.TELEPHONE POLES, F. L. Rhodes and R. F. Hosford. v. 34, 1915. 7, 1928H30. CONTINUOUS WAVES IN LONG DISTANCE RADIO TELEGRAPHY, L. F. Fuller. 72. THE PLANNING oP TELEPHONE EXCHANGE PLANTS, W. B. Stephenson.V. 34, 1915. v.47E1928S31. THIE DESIGN OP TRANSPOSITIONS POE PARALLEL POWER AND TELEPHONECIUTS,H.DESIGNOoFRANSPOSITIONFne. V 73. TANDEM SYSTEM OF HANDLING SHORT-HAUL TOLL CALLS, F. D. WheelockCIRCUITS, H. S. Osborne. v. 37, 1918.

and E. Jacobsen. v. 47, 1928.

32. TELEPHONE REPEATERS, Bancroft Gherardi and Frank B. Jewett. v. 38, 74 ELECTRICAL AS TO NAVIGATION Robert H.lg99.33. RADIO TELEPHONY, E. B. Craft and E. H. Colpitts. v. 38, 1919. 75. USES OF RADIO AS AN AID TO AIR NAVIGATION, J. H. Dellinger. v. 48,

1929.34. TRANSOCEANIC RADIO COMMUNICATION, E. F. W. Alexanderson. v. 38, 76. CARRIER TELEPHONE SYSTEM POE SHORT TOLL CIRCUITS, H. S. Black,

M. L. Almquist, and L. M. Ilgenfritz. v. 48, 1929.35. APPLICABILITY OF AUTOMATIC SWITCHING TO ALL CLASSES OP TELEPHONESERVICE, A. B. Smith. v. 38, 1919.

Clark and C. W. Green. v. 49, 1930.

36. PRINTING TELEGRAPH SYSTEMS, John H. Bell. v. 39, 1920.78. A GENERAL SWITCHING PLAN FOR TELEPHONE TOLL SERVICE, H. S.

37. SOME PHASES OF RAILROAD TELEGRAPH AND TELEPHONE ENGINEERING, Osborne. v. 49, 1930.Stanley Rhoads. v. 40, 1921. 79. RADIo TELEPHONE SERVICE TO SHIPS AT SEA, William Wilson and Lloyd38. CARRIER CURRENT TELEPHONY AND TELEGRAPHY, E. H. Colpitts and Espenchied. V. 49, 1930.0. B. Blackwell. v. 40, 1921.39. KEY WEsT-HAVANA SUIBMARINE TEBLEPHONE CAB3LE, SYSTEM, W. H. 80. SYMPOSIUM ON TRANSATLANTIC TELEPHONE SERVICE. V. 49, 1930.

Martin, G. A. Anderegg, and B. W. Kendall. v. 41, 1922. 81. AIR TRANSPORT COMMUNICATION, R. L. Jones and F. M. Ryan. v. 49,40. PHILADELPHIA-PITTSBURGH SECTION OF THE NEW YORK-CHICAGO CABLE, 1930.J. J. Pilliod. v. 41, 1922. 82. THEi ELECTRICAL ENGINEERING OF SOUND PICTURE SYSTEMS, K. F. Morgan

41. PRINTING TELEGRAPH SYSTEMS APPLIED TO MESSAGE TRAFFIC HANDLING, and T. E. Shea; v. 49, 1930.A. H. Reiber. v. 41, 1922. 83. DIAL TELEPHONE SYSTEM SERVING SMALL COMMUNITIES OF SOUTHERN

42. RADIO TELEGRAPHY, Guglielmo Marconi. v. 41 (JI.), 1922. CALIFORNIA, F. 0. Wheelock. v. 49, 1930.

43. ACHNESITCING ELEHON SYSEM OE LRGEMETRPOLTAN 84. SYMPOSIUM ON COORDINATION OP POWER AND TELEPHONE PLANT. V. 50,

AREAS, E. B. Craft, L. F. Moreboisse, and H. P. Cbarlesworth. V. 42, 1923. 19.44. TRANSATLANTIC RADIO TELEPHONY,H. D. Arnold and Lloyd Espenchied 85. THE NEWPOUNDLAND-AZORES HIGH SPEE:D DUPLEXC CABLE, J. W. Milnor44. RANSTLANICRDIO ELEPONY,H. D Arn1d ad Llyd Epencled and G. A. Randall. V. 50, 1931.

V. 42, 1923.a45. TEWVANEN-NE TYEOP HIGHLY DIRECTIVE ANTENNA, 86. MODERN PRACTICES IN PRIVATE WIRE TELEGRAPH SERVICE, R. E. Pierce.H. H. Beverage, C. W. Rice, and E. W. Kellogg. v. 42, 1923.' V-5 13

46. ELEPONERANMISSON OER ONG ABLECIRCITS A. . Clrk. 87. THE TIME FACTOR IN TELEPHONE TRANSMfISSION, 0. B. Blackwell. v. 51,V. 42, 1923. 1932.47. PUBLIC ADDRESS SYSTEM, I. XV. Green and J. P. Maxfield. v. 42, 1923. 88. VERTICALLY CUT SOUND RE;CORDS-RECENT FUNDAMENTAL ADVANCES IN

RECORDING AND REPRODUCING SOUND USING VERTICAL UNDULATIONS ON A48. ELECTRICAL LOUD SPEAKERS, A. Nyman. v. 42, 1923. DIRE, H. A. Frederick and H. C. Harrison. v. 51, 1932.


89. TELEPHONE HANDSET-A PRODUCT OF RESEARCH, W. C. Jones and 93. RADIO PLANT OF R. C. A. COMMUNICATIONS INC., H. H. Beverage, C. W.A. H. Inglis. V. 51 (ELEC. ENOG.), 1932. Hansell, and H. 0. Peterson. v. 52, 1933.

90. WIRE COMMUNICATION AIDS TO AIR TRANSPORTATION, H. H. Nance. 94. SYMPOSIUM ON RAILROAD COMMUNICATION AND) SIGNALING. V. 52, 1933.

v. 51, 1932. 95. RADIO AIDS TO AIR NAVIGATION, C. F. Green and H. 1. Becker. v. 52,

91. REPORT ON TELEMIiTFRING, SUPERVISORY CONTROL AND ASSOCIATED 1933.

COMMUNICATION CIRCUITS. V. 51 (ELEC. ENGG.), 1932. 96. CARRIER IN CABLE, A. B. Clark and B. W. Kendall. v. 52, 1933.

92. SYMPOSIUM ON TRAFFIC SIGNAI.ING SYSTEMS. V. 51, 1932, 97. SYMPOSIUM ON AUDITORY PERSPECTIVE. V. 53 (ELEC. ENGO.), 1934.

A modern manual sub-scriber switchboard of _i1922. A portion of oneof 160 switching units inNew York City (includ-ing both manual and dialsystem offices) oF typesdesigned For a capacityoF about 10,000 lines

each l l _

View of panel central office switchroom of

p ~~~selector frames oF the panel type which per-; ^ ~~~~~~~~~~~formthe functions carried out by operators in

manual switchboards. Picture shows a smallportion oF apparatus For one 10,000-line unit

Milwaukee central office of1883 serving about 700 linescover~ing the entire city.Switchboard equipped withannunciator type line signals


communication-past and present

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