BelllAboratories RECORD 228 Memory Devices R. H. Meinken and L. W. Stammerjohn Two magnetic memory devices, the permanent magnet twistor and the ferrite sheet, VIIlllm,' ;'.1 • Number 6 • June 1965 store the operating intelligence of the system. 236 The Switching Network A. Feiner A very flexible network, it is actually a cross between electromechanical and elec­ tronic, rather than fully electronic, techniques. Contents 241 Mechanical Design D. H. Wetherell Because its great flexibility stems from the stored progmm, No.1 ESS needs fewer equipment options than any present system. PAGE 246 Power System and Ringing and Tone Plants J. W. Osmun and J. R. Montana 194 Introduction W. A. Mill' N,ti,. Solid state devices help simplify the power system and lead to the introduction of Presentin!J an ;XXII,' '11/. III" No, 110:1''1'11'111/;,' S"';I"/,;II" S,/"",,,, ,/1,,111,,· If'rlmolo!lical precision dial tones and call progress tones. and scientific d;IIWl,';1I //'11;/'11 ;1//"'" /'/1/H"';I''''', 251 A New Approach to System Maintenance R. L. Campbell and W. Thomis 196 The Evolution of Telephone SwikhinJ( 11'. Kf'ilft,·,. Automatic maintenance programs comprise over half the contents of the stored pro­ 'I'f~'VoIIII;on Seemingly a ;11 11'/,,/,11111/" "/1"',.",,, . .VII, 1 1o:SS ;" 111'1111111" HilllfIl'tdy in the gram and make No.1 ESS a "do-it-yourself" machine. tradition of cmnmon ('/11/1,.,,1 H//';lrll;"1/ "/1",,.1/,,,. 257 Some Magnetic Materials D.H. Wenny 204 From Morris to Succa.~unn8 fl. W. Kl'lrhl,·,II/'· A new alloy was created whole cloth for the ferreed switch while two older ones got All the vast chant/"x XI'III/I'III;/lli III,! MII,.,.i" 11'",1 11'11/11 II,,· SIl/·'·I,..~lIuua office were an entirely new magnetic dress for the twistor memory. made to enhance .~tol'l~d 1'1'11111"/1" "0/1/1'01, 262 Semiconductor Devices M. L. Embree and J. Sevick 210 Features and Service .J . .1. YoHtllill,! There are hundreds of thousands of transistors and diodes in the system, but a The stored program. 1I1';nllx nt'tiI "",.v'r,." III Ilt'll S/I"'I'/II "IIHIOI//f'I'X and adds new mere handful of basic types serve all system functions. flexibility to many tnulitimwl xI/xII'/II "·"'''I'I'x. 268 Testing the System R. S. Cooper 214 The Stored Program fJ. /I. Sil'fI,·t, .1,.. 11/1'[ S. Siff,,'" Before No.1 ESS can be tried for the simplest kind of call, it must be tested and Many functional prog'l'am.~, 1Iuildinll 1Il0rh'x 0111,,' Hlllrt'd 11I't1//I'UIn, guide each step evaluated as a machine for executing programs. the system takes in procl'.~.~inf} ('flUX 111Id /II",/0I'IIIi1ll/ IlI/IOlI/llli/' maintenance. 274 Cut-Over at Succasunna 222 The Control Unit A. H. DotJltnaie,. On May 30,1965 in Succasunna, New Jersey, 20 years of research and development The executive part of the systWllt, it interpl''''x ittHi 1'''''' illn.~ lind data from the stores were realized in the Bell System's first commercial electronic central office. and generally keeps things runnin!/. Devices on this month's cover are all components of the sole subject of this issue: The No.1 Editorial Board G. C. Dacey, Chairman • \Y. M. Bacon • F. H. Blecher • W. A. Cornell Electronic Switching System. From the ferreed A. E. Joel, Jr. • M. V. Mathews • H. G. Och • H. A. Stone switch and the ferrite sheet (large and very small squares at the right) to the logic circuit Editorial Staff B. E. Strasser, Editor • M. W. Nabut, Managing Editor G. L. Bromleigh, Jr., Assistant Editor • J. C. Smith, Jr., Assistant Editor (extreme left) and the ferrod sensor, all are • F. E. Piellusch, Art Editor • T. N. Pope, Circulation Manager Cover unique devices in telephone switching. A part THE BELL LABORATORIES RECORD is published monthly by Bell Telephone Laboratories Incorporated of the twistor memory occupies the center of 463 West Street, ~e~ York, N. Y. 10014, J. B..FISK, P~esident; K. PRINCE, Secretary; and T: J. MONTIGEL: the picture. This device holds the stored program, Treasurer: SubscnptIOn: $2.00 per year; ForeIgn, $2.90 per year. Checks should be made payable to Bell a set of instructions that shapes the system's Laborator~es Record and addressed to the Circulation Manager. Printed in U. S. A. © Bell Telephone responses to the requests of telephone customers. LaboratOrIes, Incorporated, 1965. (Cover painting by Paul Lehr.) Electronic A Score of Tears of Organized Attack It was inevitable that modern electronic technol­ is an over-all uniqueness of the system to which our partnership with Western Electric has grown ogy would be applied to the switching machines of your attention is directed for a moment. Compare steadily broader and deeper as WE ha produced, the telephone plant as it has to the transmission net­ o. 1 ESS with earlier switching systems. in hardware, Bell Laboratorie ' de igns of apparatus work. There is nothing casual or haphazard, how­ The manual telephone switchboard was designed and equipment, and delivered on tough chedules ever, in the form that electronic switching has on the prior decision that switching would be ac­ to meet dose deadlines. The under tanding, the taken in the Bell System nor in the date of its ap­ complished by a human operator manipulating give-and-take; and the real cooperation in chi un­ pearance as an operating office serving telephone plugs, jacks, and keys. Step-by-step switching was dertaking have been marvelous to behold. customers. This program has been the largest sus­ based on the prior decision that switching would be While the big effort f the operating companies tained Bell System development effort toward a accomplished with step-by-step switche controlled in the u e of electronic witching office to erve single goal ever undertaken by Bell Laboratories. directly by the pulses generated a the customer our cu tomers better i yet to come, many operating Prior to World War II various individuals had dialed. Likewise, panel and cro sbar witches were company people have made individual contribu­ given thought to the possibility of an electronic chosen as the central building blocks for those sys­ tions to the development and de ign effort. Others switching system. Note that this was years before tems. In the case of electronic switching sy terns, are preparing them elve to plan and operate o. 1 the transistor was invented or named. Immediately no such prior decision wa made. Compare one ESS office in their territories. The ignificant con­ after the war, we organized a switching research aspect of No. 101 ESS (RECORD, February 1963) tribution of the operating companies to date has effort to explore ways in which the evolving tech­ and No. 1 ESS. Both sy tems use much common been the coordinated planning to in tall No.1 ESS nology could be usefully applied to the problem of type of equipment. But o. 101 ESS uses time di­ offices throughout the country a fa t a equipment witching telephone calls. In 1953 an electronic vision switches, and No. 1 ESS space division. is made available by the We tern Electric ompany. switching organization was formed in the Develop­ \'<7hen work on electronic switching started, we There i no better example of the neces ity for ment Area, hopefully looking toward a practical understood the principles of common control and and the benefits derived from the a ociation of the electronic switching telephone office. The 12 years its huge advantages. We believed that electronic research and development people, the manufactur­ since 1953 divide into two periods of a half dozen circuits would operate with such high speed that a ing and installation group, and operating com­ years each. The first culminated in the Morris, Illi­ single concrol would serve even a large office, and pany people than this Bell Sy tem achievement of nois, experimental trial office; the second, in the we saw the advantage in this, as distinct from a a common goal of better telephone service in Succasunna, New Jersey, office, giving commercial multimarker arrangement where competition arises timely fa hion. service. Thus, we come to the fruition of 20 years between them. Further, we dearly recognized tb,e This post-war score of year ha brought rapid of Bell System organized effort directed toward an usefulness of large memories with hort access progress in switching technology. ot the least i electronic switching system. times. But the important decision to use memory to a kind of intellectual and organizational maturity The final phase of the effort-the creation of the tore tbe ystem logic evolved as the development which allow the de igner to proceed in orderly detailed design information, fabrication of the first work progressed. fashion from the requirement to be met to the models, tests of the hardware and software-was There are two new and fundamental character­ choice of sy tem and apparatu to meet the tated started in 1959. In the fall of that year, we set the istics of electronic switching: the high speed elec­ objectives. ervice to our en tomers will benefit goal of mid-1965 as the date for the first cutover. tronic central control, and the use of memory to greatly from thi maturity. Bell Laboratories people engrossed in this project, store the ystem logic which in turn determines, view with some pride and much satisfaction the in detail, how the office will perform its functions. successful meeting of this schedule date.