Reference / Paper · 1917
Automatic Telephone Practice (6th ed.)
Early practical text on automatic (Strowger) telephone systems.
Reference / Paper · 1917
Early practical text on automatic (Strowger) telephone systems.
We : i vu i} , i) Md j i! (nnPM ; ' } j Le} t oo mei ‘ { Wha) ,Hdihy Gy y diy yh i} lata 1a, liel fi teafalas vita yays an \yn fari rey at Sth Ghee jiy ay nsite it i f J }I i} ' rity bien NR telephone Automatic 2 Pre * 21,385 N45 PUBLIC LIBRARY Fort Wayne andAllen County, Ind._ EXTRACTS FROM RULES A fine of two cents a da: . shall be paid on each volume not returned when wis Card holders must mptly notify the ko Injuries to books, and must be made good. ibrarian of change of residence under penalty of forfeiture of card. EXTRACT FROM STATE LAW Whoever shall wilful- ly or / mischievously, cut, mark, mutilate, wri in or upon, or otherwise f / Seiace any book, magazine, newspaper, or other property | | of A era under laws of this state, shall be || || the fined not less than ten dollars _ ‘§| nor more — losses book is due. than one hundred = Cc) =O. c= ae On =~ O22 ac <C C> AUVUPLTiem DISCARDED y the Interne in 2026 https://archive.org/details/automatictelephoOOOOharr AUTOMATIC TELEPHONE PRACTICE SIXTH EDITION BY HARRY E. HERSHEY BLACK GOLD PRICE $6.00 (We pay Domestic Postage on Prepaid Orders) Published ‘‘TECHNICAL By- PUBLICATIONS’’ WHITEWATER, P.O. BOX KANSAS. 68. COPYRIGHT, COPYRIGHT, COPYRIGHT, COPYRIGHT, 1917, 1919, 1920, 1924, By Harry E. Hershey COPYRIGHT, 1946 COPYRIGHT, 1949 By Mildred Hershey Donna Hershey Printed and Bound in the United States of America 665247 - VERTICAL OFF-NORMAL VSPRINGS —.._-_- VERTICAL RATCHET ——~ RELEASE ROTARY ARMATURE BACK STOP ROTARY PAWL GUIDE——~ ROTARY RATCHET oe ra DOUBLE “E LINK DOG ">> ROTARY MAGNETS ~..__ ROTARY PAWL FRONT STOP SWITCH SHAFT PLATE FRAME | ——— BANK ROD This Universal Switch may be A -Strowger Switch Mechanism. ctor, and used as a Line-Finder, as a Selector, as a Conne as a Remote Control Unit. SWITCH MOUNTING RELAYS - VERTIICAL OFF--NORMAL SPRIN GS — 7 RELEASE - SIGNAL SPRINGS seat | VERTICAL INTERRUPTER PeCniINGS |__ SWITCH MECHANISM ROTARY INTERRUPTER eee — PRIVATE WIPERS —— et ere Le —VERTICAL BANK | VERTICAL WIPER ON PLATE B ~ Strowger Line-Finder Switch. This REL WIPER switch CORDS accomplishes a connection in two motions - first the ‘‘vertical’’ motion and R O N Y A e e e a 35 34-7 36-37 38 39 40 32 41 42 45 ° 44 43 PLATE K - Strowger Mechanism Used As A Remote Control Unit. cirA dial permits remote control of - Equipment at Control Quarters. ol Contr at ator oper an operation by cuits incidental to radio transmitter with r mitte trans nt dista on of the Quarters. A handset permits modulati ters. A dial chart exhibits infor Quar ol Contr at g speech input originatin of ose purp the for h switc on Strowger mation for dialing into-the two-moti setting up various circuit combinations. ates as on. The Strowger switch (45) oper - Equipment At Transmitter Stati operate 43) (42, ys rela The interlocking described in Sec. 324(a), page 86. as described in Sec. 324, page 86. FOREWORD ‘Way back in the early twenties, I had the job of teaching a group of students some of the basic principles of the Strowger System. I found it a rather discouraging task. After. wearing my fingers to the bone with chalk and blackboard, and talking myself hoarse for an hour trying to explain how a connector works, I turned to the class expecting to find some glimmer of comprehension. Blank stares were all I got; and the only remark, ‘‘Looks like a lot of spaghetti to me’’. To this day, I can’t look at a circuit without thinking of spaghetti. FOREWORD Those who are familiar with the Sherlock Holmes tradition may recall that Doctor Watson once attempted to catalog Holmes’ personal and professional abilities with the intent of finding out just what useful purpose Holmes could possibly serve in a civilized society. After making a categorical listing of the topics on which Holmes appeared to be best informed, the good doctor, in despair and frustration, threw the list into the fire, unable to reconcile those abilities with any well-defined human need. Not long after this, Hershey had the job of teaching a similar class, and one day I sneaked in to watch him suffer. But he wasn’t suffering. He was enjoying it; so were the students. They showed not only keen interest but also a fair degree of comprehension. Some of them, by the way, were Western Electric employees, which, according to Hershey, didn’t make the job any easier. So it appears that one of the qualities that Hershey has is what might be called the ‘‘pedagogical instinct’. Perhaps there is something of that nature in his book. I sincerely hope so, although I have no intention of reading it to find out. I once tried the same sort of experiment with Harry Hershey, and the results seemed to me equally fruitless. He is the first to admit that he can’t write. Often, when he has asked me to edit his work - and Heaven knows it needs editing - he has said to me, ‘‘How in thunder did I get into this writing game anyway ?’’ His phrasing is at once amateurish and pedantic. He has a casual disregard for ordinary syntax. He uses punctuation not to make sense, but merely to break the monotony of words. His spelling has neither the charm of originality nor the consistency of being phonetic. True, he knows something about the telephone business, but then so do thousands of other people. But perhaps Hershey’s greatest saving grace is his sincere and unbounded admiration for the Strowger System, which is the sole subject of his book. He has worked with it, and with the people who made it what it is, ever since his days at the Kansas ‘‘cow college’’. He has seen other systems come into being and struggle vainly for supremacy, but to Hershey the Strowger System still towers far above them all. We have no disposition to argue with him on that point, and the occasional brave soul who suggests that he ought to say something about newer systems gets a rebuff that is characteristic of Hershey in his less gentlemanly moments. Now I submit there is nothing in all this that might plausibly support the premise that Hershey has any business in publishing a textbook on Automatic Telephony (or anything else for that matter), or that his success in that venture would have been so great as to stir him to the publication of a sixth edition. Apart from all this, Hershey’s book is quite unlike any other technical book I ever saw. It may well be that I had something to do with that too. I remember saying to him one time, ‘‘Harry, next time you publish your book, put something in it besides the dry-as-dust mechanical and circuit details that other books on telephony have. Bait it with some human interest stuff that will get people to read it.”’ Now my remark was made in perfect innocence and good faith, and I wasn’t suggesting that he should go berserk the way he did with his fifth edition, using it as a crusading vehicle for his amateurish political philosophy, most of which I am inclined to think is a cloak for his own laziness and ineptitude. Perhaps he has concluded that such vaporings have no place ina technical book. Whatever the reason, you won’t find much of it in this edition. Anyway, if Hershey thinks this Foreword is a better space filler, who am I to argue with him? But facts are stubborn things! This is the sixth edition, and Hershey doesn’t publish his book for sheer pleasure. While I expect a complimentary autographed copy in return for this frank Foreword, I warrant that few others will be so favored. Make no mistake about it; Hershey will make money out of this edition, just as he has out of all the others, despite his frequent ravings against the fruits of private enterprise - that is, the other fellow’s private enterprise. Well, just what is it that Hershey does have? Why is he able to continue selling this book of his? I can think of several possible explanations. One is that the telephone industry has never been singularly favored with good textbooks; which is another way of saying that Hershey hasn’t had much competition. The plain fact is that there hasn’t been a really well-written book on Telephony since McMeen and Miller’s 1912 edition, on which I cut my own eye teeth. But, after all, what you will want to know most about this book is whether you are going to get your money’s worth. My guess is that you will. But if you conclude otherwise, don’t try to get your money back. I forgot to mention that Hershey is also qualified to practice law. But I don’t want to rob Hershey of all the credit for his success in the publishing game. One thing in his favor is that he undoubtedly has a flair for teaching, which is excellent background for the writing of any technical treatise. Here’s a bit of history to illustrate what I mean. La Grange Park, Illinois February 10, 1949 vi H. E. Clapha ae FOREWORD PREFACE TO SIXTH EDITION The present high price of paper and composition very definitely limits the number of pages that can go into a text book to sell at an established price. For this reason ‘‘Caveat Emptor’’ and the non-technical sections of ‘‘Part B - Historical’’ have been deleted to make way for more technical matter in the Sixth Edition of this text. So much remains to be said and so few years are left the writer, that it seems expedient to follow the plan of the earlier editions - significant fundamentals plainly presented in order that the student may acquire a background which will permit later specialization in his chosen branch of the art. The Sixth Edition is greatly enlarged (256 pages as compared with the 160-page fifth edition), and actually presents 112 new pages covering circuit and technical discussion. The new coverage includes, among other things, complete circuit descriptions of a typical Local Test Desk and associated switch train, a toll switch train and many special connectors. y of Appendix ‘‘G’’ - Typical Adjustments, made possible by courtes the for ion informat of wealth a presents , Company Electric Automatic details. student who is interested in mechanical of the telephone Appendix ‘‘H’’ - Elementary Principles, discusses elements Strowger telein used as instrument, the Strowger mechanism, and relays phone practice. ration in the general The appendixes became available too late for incorpo the special index on and XVI page on s content of index, but see the table page G-00. about in the Foreword? By the way, just what is this sin tax that Herb. talks Could it be a new Federal tax? Harry E. Hershey Chicago, Il. March 1, 1949 vil OF TABLE Part A. PART 123 AUTOMATIC TOLL BOARD 124 AUTOMATIC TOLL TICKETING 125 THE.G: Aux 126 THE CALL INDICATOR 127 CLASS OF SERVICE TONES 128 128(a) CODE CALL SERVICE : Code Call Via The Connector FA 3 129 COMPLAINT 3 130 THE 131 CONFERENCE A - GENERAL SECTION PAGE 100 SUBSCRIBER STATION EQUIPMENT 101 THEDIAL . 1 102 102(a) GROUPING OF SUBSCRIBERS Illustration . 2 2 102(b) 102(c) Proscess of Elimination Million Number System 102(d) LetteredDial 102(e) Smaller Systems . | 5 . . STROWGER MECHANISM 104 THE STROWGER 105 STROWGER 106 106(a) NON-NUMERICAL SWITCHES Strowger Line Finder 107 FINDER-CONNECTOR 108 FINDER 109 THE 200-LINE FINDER BANK : . CONNECTOR . : LINK . = SELECTOR 111 THE 112 112(a) TRUNKING WITHIN THE OFFICE Grading 113 INTER-OFFICE REPEATER Ad 4 131(c) ‘Fixed Group”’ 4 132 132(a) CONNECTORS OF LARGE CAPACITY . 1 Wiper Selection Made at Banks 1 Of Preceding Switch Wiper Selection Made Within Connector : <a By use of Counting Relays 1 By Use of Minor Switch 200-Line Connector Having 20 Rotary Steps ua] 115 THE 116 THE TOLL LOCAL tl 133(b) CONNECTORS OF SMALL CAPACITY Using 11-Point Rotary Switch Using 25-Point Rotary Switch 8 134 134(a) CONVERSATION TIMING . Link Timing (Line Lock Out) 135 DIAL 9 136 9 136(a) 136(b) DIRECT LINE SERVICE. Executive Key-Calling Service Executive Loudspeaking Direct Line System . 8 9 TRUNKING . 10 CONTROLLED RINGING 10 137 DISCRIMINATING TRAIN 10 138 EXECUTIVE “‘RIGHT OF WAY” 138(a) SERVICE 10 138(b) Using Individual Connector Using Common Connector 10 139 FIRE ALARM AIR CONDITIONING 10 140 FLOOR 120 120(a) ANNOYANCE TRAP Fire or Police ileal 11 141 IMPULSES, 142 121 ASSISTANCE 11 INFORMATION 122 122(a) 122(b) 122(c) AUTCMATIC SWITCHING OF TOLL LINES 11 Loop Dialing 11 Composite Dialing Ly A. C. Dialing 11 143 INTERCEPTING SERVICE 144 LINE & TRUNK STANDARDS 145 LOCK I Aly/ THE 118 PARTY 119 122(d) TEST SWITCH LINE ; . TRAIN SWITCH SWITCH 132(b) 132(c) 132(d) 132(e) Progressive 133 °133(a) The Director TRAINS SERVICE ‘Meet Me”’ 7 STROWGER SWITCH CONDENSER 131(a) 131(b) 7 110 114 OBSERVATION 3 5 6 DISTRIBUTER IMPULSE . 3 103 113(a) re CONTENTS TRAIN SERVICE SERVICE Voice Frequency Dialing 11 PLANS LIGHT PULSING & HEAVY SERVICE . . 1! TABLE MESSAGE OF WATCHMENS SERVICE P.A.B.X. Recording Type 17 174 174(a) 174(b) iz REGISTERS Combined Recording & Supy. Service THE MINOR SWITCH MONITORING SERVICE 18 175 MARKINGS 18 175(a) 175(b) CONNECTORS PECULIAR TO P.A.B.X’s Impulse Repeating on Trunking Levels” Switching through on Trunking Levels . 176 CALL INDICATOR 177 THE 178 178(a) 178(b) 178(c) KEITH LINE SWITCH Line Switch Mechanism Master Switch Mechanism Line Switch Boards . 179 ROTARY 180 180(a) SECONDARY LINE SWITCH Method of Trunking to Secondary MULTIPLE . CONTENTS 151 OUTGOING SECONDARY LINE SWITCHES PAY STATIONS 152 152(a) THE P.A.B.X. : Passing Call Feature 153 153(a) 153(b) 153(c) THE: Pi AsX.. Small P.A.X’s. . Moderate & Large P. A. x’Sh Special Services 154 PICK-UP . ‘ SERVICE NIGHT ANSWERING AND TRANSFER SERVICE POWER . The Battery, and Voltage Control . End Cells Counter Cells Full- Float Operation High- Low-Voltage Controlled Charging Battery Eliminators of the Battery Functions . LINE EQUIPMENT SWITCH LINE SWITCH Line Switches 180(b) Primary to Secondary Line Switch Combinations OUTGOING SECONDARY 181 181(a) 181(b) LINE SWITCHES Used With Selectors Used With Switching Selector Repeaters 31 182 LINE ADAPTORS 183 CALL THE R.C.X. 184 184(a) RADIO INTERFERENCE 184(b) I.D.F. FACILITIES LINE Cabling Plan Without Line I.D.F.Facilities F. L.I.D. Facilities Increase in Efficiency of 32A Outside Plant Re-Distribution of Originating Traffic 32A Reduction in Amount of Line 32B Equipment Required in es Chang for sions Provi 32A Classes of Service 32A . Plans L.I.D.F. 32B Typical Full L.I.D. F. Plan PRELIMINARY PUSH IMPULSES RINGING BUTTON THE RELEASE LINK RESTRICTED SERVICE REVERTING (D) . 184(c) 184(d) SERVICE OBSERVATION SIMPLEX DIALING SLUGLESS PULSING . 185 185(a) TRUNK TERMINATION Termination on Subscribers . 185(b) EQUIPMENT (A) (B) 185(c) Line Equipments . Incoming Switch Termination Method Discriminating Service Universal Numbering Comparative Advantages 186 186(a) RACK MOUNTED EQUIPMENT Details of Trunking . 187 DIAL-BACK RING SUPERVISORY TIME (B) (C) CALLS THE ROUTINER SPLASH (A) RECORDER SERVICE TONES TRAFFIC METERS TRAFFIC STUDIES ix EQUIPMENT 32B 32B .32C .32D 32C 32C 32C 32C .32D TABLE Part B. OF CONTENTS PART B- HISTORICAL SECTION 200 oie SUBSCRIBER STATION EQUIPMENT THE DIAL : 209()) c Delayed Impulse Dia Wim 201(d) | Thousand Year Dial 201(e) Quieted Dial 201(g) Autodial 201(f) 44 Line Relays 44 Line Finder Group Relays PAGE 209(m) Distributer . 33 a 210 210(a) 45 SELECTOR 210(b) - 33° 23 210(c) 210(d) Searching For Absence of Ground . Battery Searching 210(e) Stopping on First Idle Trunk 33 Sanitary Dial STROWGER Cut-In . 44 45 . , etl -2:10(f) Automatic Rotary : 210(g) 34° 210(i) 34 210(k) Digit Absorbing Selector . 210(k) 210(j) By ‘‘Pull-Up”’ of Relay —-Powell Selector. 45 45 45 . 46 46 ; 10/20 Selector . 45 . 45 45 By De-Energization of Relay - 33° - 34 . Functions 209(k) 209(1) 201(a) | Non-Returnable Dial . Beit) pear ee eimai 44 . Distributer 209(h) 209(i) 46 46 Major Functions of Selector 46 202 GROUPING OF SUBSCRIBERS 203 STROWGER MECHANISM - 340 211 THE IMPULSE REPEATER 46 203(a) B.P.O. Version » 35 211(a) One-Way Impulse Repeater 47 a . 204. THE STROWGER BANK 204(a) §Mahoney’s Switch 5 . 36 gS af211(c anie ron Se Two-Way 204(b) Three 200-Contact Banks , Michrophonic Noise 36 SH: sclaciinee 36 211(f) Switching Selector Repeater B.P.O. 36 211(g) 36 36 aint 211(}) Sauer Functi 211 (ik) Citations 204(c) 204(d) Switch ‘ ° & Bank 205 205(a) STROWGER CONNECTOR Connector Functions . 205(c) Sequential Operation a - . 37 205(e) 205(f) 205(g) Connector Normals, Open or Closed Testing Called Line For Busy Prevention of Further Rotation 37 37 1, eu 205(b) 205(d) Seizure ys F As AE Connecting Wipers to Called Line 205(h) Ringing the Called Line . 205(i) Ringing Generator ‘ 205(j) 205(k) Battery or Ground Connected = Instantaneous Ring-Cut-Off 205(m) 205(n) 205(0) 205(p) 205(q) Draining Condenser Charge Answering Supervision Booster Battery Metering Last Party Release of Connector First Party Release of Switch Train , . 205(1) | Ring Back Tone . 206 STROWGER LINE FINDER . The 100-Line Finder 206(a) 206(b) 206(c) Preferential Hunting . ) Dial Tone FINDER-CONNECTOR LINK FINDER DISTRIBUTER 209(a) 209(b) 209(c) Preferential Hunting Theoretic Grouping Actual or Numerical Crone 209(d) 209(e) Mechanical Arrangement Line Relays 209(g) : . 37 Line Finder Group Relays Trunk 211(h 211(1) eee 212(b) T 37 38 212(e) 212(f) eqns = eee 39 mes : ad ; — Gradin ey ) 213 (b) (A) (higae0) (d) 213(e) a ae slpereeenats School PE On ne RUNING : pb Secondary Line Switches = petectan Illustration epee Interconnection, Auto. & Manual Manual to Automatic Automatic to Manual Universal pies & eet Absorption Citations SWITCH TRAINS . At "49 42 grain) 15(b) Regular Straight Line Connector Local Trunk Hunting Connectors With Night Service Feature 2 44 (C) (D) Number Assignment ue ot 50 au sta. 743(8) 714 44 44 fe bli 5 19(2) sa ee 8 ia nt ee _ 1K 49 49 44 , en beieteiarnla Leen Sli Bate Sh 1 : p19(¢) 40 47 True Tee-Way Impulse Repeater . 212(d) 36 re 47 : 37 39 pe ee h . 38) te epea nf Economy . 37 P38 38 38 38 38 R ~ 213(f) 207 208 209(f) acer lse : I retat pegtaa vit 46 Hunting Function 50 oY 51 51 51 52 53 93 53 54 54 55 56 56 56 56 nother Method Establishing Groups 56 Nigh t Service forofP.B. x. Trunk Groups 56 TABLE 215(c). (A) 215(d) 216 216(a) OF Conn. Having Night Service Feature . Conn. Without Night Service Feature . Groups of More Than Ten Trunks But Not to Exceéd Twenty . Disconnect Supervision to Called Manual Exchange Local Level Hunting Connectors With Night Service Feature Number Assignment. ‘ Bank Arcs . CONTENTS 218(d) (A) (B) (C) (D) 56 57 57 57 Toll Connector 216(c) Combination Local & Toll Regular Connector 216(e) 217 . 293 of Test Connector 293(b) Release of Test Connector Only, or Release of Entire Train Verification Service Verification Circuit Test Connector . Combination Local & Test Connector PARTY LINE SERVICE Terminal Per Station Service Two-Party, Divided Ringing, Selection Made in Connector Bank, M.A.X. As Above, For P.A.X’s ; Five-Party Harmonic, Metallic Ringing, Selection Made By Preceding Switch Two-Party Divided Ringing, Selection Made by Preceding Switch Terminal Per Line Service © ' Two-Party, Divided Ringing Frequency Selecting Connector Frequency Selection Last 294(a) 294(b) 294(c) 295 295(a) 295(b) 296 297 Reverting Calls By Special Number By Prefix to Directory Number By Directory Number xi . 65 : . 65 65 . . 65 KEITH LINE SWITCH 3-Wire Line Switch . Single Coil Line Switch 2-Coil Line Switch , Self Aligning Line Switch 65 66 66 66 67 ROTARY 67 LINE SWITCH SECONDARY THE TEST SWITCH TRAIN Test Distributer : Test for ‘‘Busy Test Connector”? : Test Connector Becomes Idle Impulsing Test Connector Test for Busy Line Called Line Becomes Idle Rotation ; 10-Party Code Selecting mane THE LINE SWITCH Toll Break Down (Disconnect Delayed Ring ; Re-Ring ‘ Answering Supervision ‘ ; Combination Local & Toll Trunk-_ Hunting Connector Toll Level-Hunting Connector Combination Local & Toll LevelHunting Connector Further Code Selecting Connector Frequency Last Seizure Supervision Flash Busy ‘ Toll Offering Service Camp-On- Busy : 216(f) Code Ringing 64 Two Codes Only (1--Ring or 2-Rings)_ 64 The Two-Ring Connector 64 Delayed Ring THE TOLL SWITCH TRAIN Toll Transmission Selector 216(b) Part B. LINE SWITCH 68 Pick-Up Service 69 LOCAL TEST DESK Classes Of Calls . 69 69 : Incoming Calls To Test Deak Incoming Call Wire . Incoming From Selector Levels Inspector’s Trunks beatae Seizure . : Answering Holding . Release . . Test Desk Cord Circuits The Service Cord : Incoming Call, Answering Incoming Call, Extending Outgoing Calls From Test Desk Outgoing Call Wire ; : Outgoing Via Service Cord Outgoing Trunk To Test ’ Distributer (Circuit) Seizure Dialing . Testing, “Out?” Test ‘In’? Test Permanent Disconnect. Monitoring Subscribers’ Call Dialed Connector Or Line Busy . Holding Connection When Connector Is Busy. : Holding Connection On Idle Line : Releasing Connector From Busy Line. : : Release Of Test Connector Only : Release Of Test Switch Train Test Line To MDF : Test Circuits Primary Test Cord . Auxiliary Test Cord . Interchange Key. Tests. With Primary Test Cord . With Auxiliary Test Cord Testing Combinations . Testing é : : ; 69 69 69 69 69 69 70 70 70 70 70 70 70 70 70 71 ie! 71 71 71 (a vel 12 72 72 12 73 73 73 73 73 73 74 74 74 74 74 74 TABLE Part C PART 300 C CIRCUIT SEARCHING 301 301(a) 301(b) 302 302(a) 302(b) 303 304 304(a) (A) (B) (C) OF KINKS CIRCUITS : CONTENTS 322 322(a) 32.2(b) LOCK PULSING Light Pulses Heavy Pulses 32.2(c) DIAL 323 PULSE SPEED CIRCUITS ; RANGE . CUT-IN CIRCUITS INTERLOCKING RELAYS : Searching for Absence of Ground . Switch Advances Upon DeEnergization of Motor Magnet Switch Advances Upon Energization of Motor Magnet Battery Searching First Illustration . REMOTE CONTRCL CIRCUIT LOCK OUT CIRCUITS LOCK OUT CIRCUITS . IN AND OUT CIRCUITS First Illustration Wheels Counted : Direction Established Last FD Relay Operates DRIVING CIRCUITS Pulses 312 312(a) RESTORING CIRCUITS The Strowger Release Circuit 313 313(a) 313(b) 313(c) 314 315 316 IMPULSE GENERATORS Speed Pulse Ratio Impulse Generation . First Illustration Second Illustration Third Ilustration 317 318 318(a) 318(b) DELAYED RELAY OPERATION Operate Time Delay Weighted Spring Variable Resistance Around Condenser 319 319(a) RELEASE TIME DELAY Vibrating Reed . 320 COMBINED OPERATE AND RELEASE TIME DELAY 321 321(a) 321(b) PULSE REPEATER CIRCUITS Pulse Shortening . Pulse Stretching 321(c) ALTERNATE OPEN & CLOSE RELAY COMBINATIONS . COUNTING & TOTALIZING Counting Totalizing Second Illustration Searching for Ground “All Relay’’ Searching Circuit ““All Relay’’ Distributer . : Selection of Next Idle Finder Next Finder Busy : Distributer Operation When 305 305(a) 306 307 308 309 310 310(a) 311 311(a) 311(b) . First Illustration ALARM Temporator Driving Circuit 3-Wire Driving Circuit 2-Wire Driving Circuit ““All Relay” Driving Circuits. Two Relays. Per Step Second Illustration One Relay Per Step Relay Behind Cut Off Endless Counting Chain CIRCUITS NON- TELEPHONE PATENTS Numerical List of Patents STEPPING SWITCHES Around and Return Unidirectional Rotary Up. Around & Return Sequence Switch Toggle Action of Rotary Interrupter 3-Wire Driving Circuit Searching For Absence of Ground PART DEIR GUTS SUBSCRIBER STATION Nag GUETS The Dial Delayed Impulse Circuit Reading of Line and Release Relay Modern Telephone Circuit OF RELAY LINE CIRCUITS Used With Plunger Line Switch When Calling ; p Restoration of Receiver When Called ¢ : Illustration of Closed Normals As Above But With Open Normals Used With Non- Homing ees Line Switch . Used With Rotary Finder Used With Strowger Finder Line Lock- Out Circuit Xl ‘ : Jart D. TABLE OF CIRCUITS 95 CONTENTS Part D— ———————————————— a NON-NUMERICAL 02 02(a) 02(b) 02(c) 02(d) (A) (J) Self Aligning Line Switch Circuit Rotary Line Switch Circuit ‘ A Relay Assembly. : ‘ : Mechanism Functions Circuit Reading Seizure . Seeking An Idle Trunk Engaging Idle Trunk Switching Through Restoring Electrical Circuit to Normal Incoming Calls SELECTOR 103(a) Seizure 103(c) 4103(d) 403(e) 403(f) 403(g) (A) (B) 403(h) 403(i) 403(j) 403(k) 403(1) 404 404(a) 404(b) 404(c) 404(d) 404(e) 404(£) 404(g) 404(h) 404(i) 404(j) 404(k) (A) (B) 404(1) 404(m) 404(n) 404(o) 405 405(a) (G) Keith Line Switch Circuit Master Switch Circuit t03 403(b) SWITCH SWITCH CIRCUIT (H) (I) ; (J) . : : Raising Shaft & Wipers to Dialed Level Cutting In on Dialed Level : Trunk Hunting Returning Busy Tone if all Trunks are Busy Seizing the First Idle Trunk ; Release From All Trunks Busy Condition From Completed Call Permanent Alarm Selector Release Alarm . 115 115 117 117 117 .119 119 . 119 119 119 By | ae YB .121 .121 rige IMPULSE REPEATER CIRCUIT Circuit of One Way Repeater . : : Seizure. Loop to Distant Office Impulse Repeating. Talking. Circuit ; Releasing Circuit of Two Way Repeater . 122 . 122 . 122 . 122 . 123 . 123 . 124 . 124 FEATURES 125 125 125 CONN, OF UNUSUAL CAPACITY : Ten- Line System . 10-Line Connector, CIRCUIT 10-Line Finder, CIRCUIT . : Auxiliary Equipment, CIRCUIT Ringing Converter, CIRCUIT . Spark Suppresion CIRCUIT 408(b) Rotary Stepping Trunk Hunting Switching Through to the Called Line Answering . Transmission Returning Busy Tone for Busy Condition Executive Right of Way Release (A) 200-Line Connector, CIRCUIT Selection at Banks of Preceding Sw. Selection Within The Connector 129 129 130 Trunk- . Hunting Connector, CIRCUIT : : Level-Hunting Connector, CIRCUIT é ° Relay Chart . TOLL SWITCH TRAIN . Toll Transmission Selector, ‘CIRCUIT : : : Seizure Vertical Steppine= Automatic Rotary Searching . ATB, ‘‘Flash Busy” Seizing First Idle Trunk Vertical Hunting Rotary Hunting Switching Through . Selection of Next Idle Finder P Next Finder Busy Mins 130 130 131 Without Night Service Feature Second Illustration With Night Service Feature Calling Individual Line Calling Pilot Number : 128 128 190- Line Connector FINDER SWITCH CIRCUIT Finding the Calling Line . £25 126 1270 22-Line Connector, CIRCUIT By Use Of Counting Relays By Use Of Minor Switch . Release From Completed Call Calling Party Disconnects First Called Party Disconnects First Release From Busy Permanent Alarm Busy Key Spark Suppresion Seizure Last FD Relay Operates ; F Release Transferring Future Calls of ‘Group A’’ to “‘Group B” Failure of Vertical or Rotary Stepping . ; If a Finder is Free in Group B If all Finders are Busy in Group B Failure of a Finder to Find a Line Calls to the Subscriber Executive Right of Way Start & Level Marking Circuit 2 All Finders Busy More Than One Call Received ; At a Time Finder Blocked Key .. : Test Jack Spark Suppression SPECIAL CIRCUIT Busy Key Test Jack CONNECTOR SWITCH : Seizure Vertical Stepping Distributer Operation When 131 132 132 133 133 133 134 135 136 136 136 136 137 137 137 TABLE Part D (F) Completing The Connection (G) (H) Line Seizure Supervision Called Line Busy a: (1) Ringing The Called Line (J) Answering (K) (L) (M) (N) 138 (1) Release of Test Connector Only ay 138 (J) Release of Entire Switch Train : A 139 139 (K) (L) 139 Release Of Completed Connection (M) Dialed Test Connector Busy Use of Connector Selector 139 Disconnect Supervision Re-Ringing Called Line : ., Re-Ringing PBX Trunk .., (Q) Coin Controll 2 3 Toll Connector, CIRCUIT . cs i Seizure . Testing Called Line coi (C) (D) (E) (F) Called Line Free 5 Ringing & Ring-Back Tone Called Party Answers Release. , (G) Called Line Busy ; (G) (G1) (G2) (G3) Called Party First eowidcy (G4) (H) From Abandoned Toll Seizure Call A (I) () Vertical Stepping Rene stsopire : (K) Testing Called Line. (K1) Called Line Busy . Called Line Idle .- na ae (N) (0) Transmission Re-Ringing (P) oleae 1. ; ; s ; ; A : : ‘ : , ‘ ae (B) (C) Individual Conn sen? ets yan ican Toll eeepoine ‘Rotary Stepping . Called Line (D) Busy Camp On Busy. (D1) Ringing After (E) 412 412(a) (A) (B) (C) (D) (D1) (E) (F1) (F2) “ee ; Toll Ofteriugma TESTSWITCHTRAIN | . Test Distributer, CIRCUIT Serpe j oe Vertical Stepping ees . ; seh Test Connector Idle Repeating Impulses Called Line Busy CampOnBusy . , ., | ‘ , “ae. | z : . . . AS: ako . A A - 15a ~ . . . 15a 151 151 151 153 PARTY 414 414(a) (A) 414(b) 414(c) Terminal Per Station Service . Two-Party, Divided Ringing Selection Made Within The Conn, a Five-Party Harmonic : : 1-Ring & 2-Ring ., Four-Party, 1-Ring & 2-Ring aesice S 10-ee (B) tes Vertical Moti Mae. a . ion 145 (D) am a. , eae 145 (E) ike a 145 avi F ne eefeel) Called Pe Line (H) ae ete: Ba ee (H1) 152 Terminal Per Line Service . Two-Party, Divided Ringing ., Selection Made by Preceding Sw. Selection Made Within Connector Frequency Selecting Connector 145 ee \ tee: - 152 153 153 153 152 CIRCUIT . 154 A<a 5 ‘ - a 154 154 - 154 5 = . . . oe Code % ‘, é .; 2a . 155 fe ‘ae . 155 , . 155 145 (H2) He (I) Called Line Busy . , 145 ae 0) qi cae J1) Raver ung Saleey Directory Number , A > 155 , a . 156 i6 es 415(d) 146 aise) 146 ea ew (A) (e) ie ic 147 e Release , “ reneing Called Part a a eee sie ertica epping (H) 0) Transmission Bee CG : , ; Reverting Calls |) ar 417 149447 (a) Se Oe SCORLNG ig 148 148 149 am Individual Connector, CIRCUIT he 156 156 . 156 . 156 .. 156 Slee , . , ge Se . 156 , 456 F : ‘ : A » . ; « 3. : aes ugh. Ringing Called Line. a 156 Code Ringing, Push Button Controll Over-Ride Of Busy Seizing Called Line. 148 5 Code Ringing, Dial Controlled CKT. ) (E) (G) : Called Party Answers i 149 | A 413 tis Cutting-In On Dialed Line ; Testing Trunk To Test Connector its), 141 141 ve eae Lo Pan eona’s (J2) 411(d Ky Pees ko Pe - Testing Called Line Heloeee a A 145 , ale . 4 4 ° C Ch 415 415(a) (A) (B) 415(b) 1s . . 141 414(d) . pees be : Two-Party, 14 - Advancement of Wipers LINE SERVICE . . 14 samme - (B) 143 143 143 143 144 144 144 144 vr . |. . 140 145 ‘ Verification Service Test Connector, CIRCUIT Seizure . 142 : . . 3. 412(b) (A) 141 142 142 142 | C@mbination Connector, CIRCUIT Called Line Idle. In’ &*'Out? Tests 140 140 142 Local Seizure A Vertical Stepping Rotary Stepping Called Line Busy : Called Line Idle ? Answering . 3 ’ Transmission , : Release , Cullite Party aank (K2) Release Of ‘Permanent Line” , . ; - (A) (B) (C) (D) (D1) ©) (F3) (G) (H) . : 411(c) 138 138 138 Release From Busy Intercept Service (A) (B) CONTENTS ., (O) (P) 411(b) OF an , ele 157 ae Roverting Call By Special Number . 157 2-Party, Divided Ringing, CKT, | 157 TABLE OF CONTENTS Part D. in 2 tortie. Saucy | G0) uci tages 70 Trunk. Idle Seizure of First (E) Bee Ringing Called & Calling Stations 158 (c) (A) Seizure. (D) Receiver Removed (E) “ (G) ih 158 (F) : . le as ts «sy (408 . 158 a Selecting First. Frequency jsp Selecting Second Frequency . et155!) 159 (A) 3 ) (F) (G) (H) Seizure. 8(a) To Directory Number a Digit Absorption 8(c) Code Ringing 8(d) 20-Party Bridging, 10-Party 8(b) Conversation Timeing . . . 161 oe OL . . 161 161 . . . . . trot Answer Party ; mp we lens: ef A 423 424 EXECUTIVE ‘‘Right-Of-Way”’ Using eiivitaal Cones . 171 . . . 171 . cy Code Call deniite Conference Service yl tH : 422(d) 422(e) a 159 eee Party Replaces Receiver . 159 > : : R nging 260 eee Receiver Removed . 160 . Both Receivers Replaced Sa a A oy Line Lock-Out Reverting Call By Prefix 8 arith First Idle Line in Group alled 10-Party, Divided Ringing, CKT. mere Pama Releasing “ ae Line BusyHunt-The-Not- te} ©) sige All OGT Bus (G) 422(c) 158 158 . . . Both Receivers Replaced Trunk Call Rlease of Reverting Line Lock-Out Cc . : alli 158 Testing CalledLine. . «. E a 171 172 : Die «| 172 (D) (E) 4 Called Line Bus ‘“‘Over-Ride’’ CE Hees = & 7 po : (F) Camp-On-Busy , va. Using Common Connector 425 . Seizure (A) (B) (C) CODE 136 CALL 426(b) ee 173 . Seizure ae 173 SERVICE Register-Sender a ‘ Vertical & Rotary Motion. 173 426 (c) 426 (d) Operation of Sender Answering Code Call ; . 73 174 Gy maics at63 427 427 (a) 427(b) CONFERENCE SERVICE ‘“‘Meet-Me’’ Conference Fixed Group Conference 174 174 174 (F) (G) (H) nariGs . Fifth Digit Dialed . 163 Receiver Calling Party Replaces 164 . Station. Called Ringing - 164 . Answers . (D) Release of Individual 175 (J) “Timing Out?’ Progressive Conference 176 (A) (B) (C) (D) (E) (1) . ‘ Divided, CIRCUIT ‘ Seizure. iret Digit Dialed Second Digit Dialed Third Digit Dialed . Fourth Digit Dialed Called Party oe 2-4. ; : <-. 4162 ; ; : ri65 : , , 162 162 _ _ A ; (C) Testing Called Line . . 165 ~ 165 (E) (F) 177 177 , 166 (G) Ring-Back Tone. Digit Absorption. . 166 (H) Calling Other Parties 177 20 . « . : (B) Vertical & Rotary Movement (D) Code Call Circuit Free (C) (E) 21(b) 21(c) .21(d) .21(e) (A) (B) (C) Testing Code Call Circuit . : . 166 ~. + > 166 . 167 : ; Night Number Service Watchman’s Recording Service Trunk-Hunting on OGT Level Pe LO 167 BW Repeating Impulses ‘‘Meet-Me’’ Conference Service Searching For Idle Trunk Seizing First Idle Trunk (D) 121 (f) Annunciator Service 122 (a) 122(b) (A) (B) . Switching Through, CIRCUIT Discriminating Service ay (D) (I) 177 Transmission 17% 430 P.A.B.X. 431 ROTARY 168 432 THE THE MODERN Translation weeeel Ow i : : . 168 433 433(a) . . 169 433(b) 5 Peed (A) (B) (C) 433(c) 169 409 169 xv 176 177 Releasing TRUNKING, 108 . - Called Line Idle. 429 pee Outgoing Calls. Raising Wipers to OGT Level. , : Discrimination 176 TRAFFICORDER ’ : Rotary and Vertical Motion 428 38 Pe Automatic Cut-In_. Repeating Impulses 122 . (B) . 166 . 176 165 CONNECTORS PECULIAR TO PABX’S Impulse Repeating, CIRCUIT + . Code Call Service 175) Seizure. 19 (A) (E) Release of Control Station 174 175 175 (A) 165 Seizure ; Seizure... Ringing All Stations . : Transmission. ‘Station . 427(c) Reverting Call By Directory Number 21 21 (a) (A) (B) (C) 177 17% Inter-Office 177 LINE 174, SWITCH 177 DIRECTOR DE ae 5 : 178 178 Alternative Routing 178 Tertiary Routing Passing Connections . Citation . 179 179 179 Secondary Routing 179 Part D. TABLE 434 DIALING 435 DRY-TRUNK 436 LOCK 437 AUTOMATIC SWITCHING TOLL LINES OF METHODS REPEATER PULSING 179 Receiver Unit Dial. , é 179 Cradle Switch Ringer Condensers Induction Coil 179 438 438(a) STROWGER BANK. Strowger Mechanism 439 TRUNKING 440 PROGNOSTIC ATION WITHIN 180 180 180 THE OFFICE 180 180 Mobile Radio System, Ft. Wayne Intercepting Service As Applied to 180 180 180 Automatic Systems. Super-Imposed Ringing 180 180 A-000 A-100 A-101 DIxXe <*G’’ Sequence of Strowger Switch Inspection General Requirements : Bases & Busy Keys . A-110 Horizontal Relays, Single Contact A-120 Off-Normal Springs c A-121 Shaft Spring Assemblies A-122 Cam Spring Assemblies A-130 Vertical Mechanism A-131 Switch Dogs ; A-132 Rotary Mechanism , é A-133 Release Mechanism & Springs A-135 Shafts, Wipers & Banks. A-136 Minor Switch : : : A-173 Horizontal Relays, Twin Contact A-805 Dial . 5 A Telephone Circuit . Dialing Circuit Ringing Circuit . Transmission Circuit Receiving Circuit. ELEMENTARY 1.2 Oe PRINCIPLES Introduction é : Explanation of Drawings Telephone System Telephone Instrument Handset , = Ne Transmitter Unit . ‘‘H’’ : : QO aM e¢ wo eeB Functions of the Automatic Switchboard Mechanics of the Strowger Switch Switch Mechanism : : Shaft & Hub. Vertical Motion . Rotary Motion Release Action , oO> oOo i] 1 QADAAN : he , Mechanics of the Minor P29 Ww ww wo w md d ii Switch a0 Q Mechanics of the Relay . Cols : ; ‘ Heelpiece Armature Spring Assembly . Spring Adjustments Slow-Acting Relays Special Relays : : Short-Lever Armature Relay Double Armature Relay Two-Step Relay . AAQANAM Oe Ee 1m OO © OMNwrFTwin Contact Relay 1 Type ‘*Z’’ Relay. APPENDIX ; j . Switch Jacks . Relay Mountings Test Jack Busy Key ADJUSTMENTS Shelf Jacks, Covers, Co0 BW Spring Assemblies Off-Normal Springs . Cam Springs Interrupter Springs Release -Signal Springs (Courtesy of Automatic Electric Company) TYPICAL oe Pob OF Automatic Pulsing on Carrier Current Telephone Channels. Switching Selector Repeaters In Multi-Office Networks PePTN CONTENTS ‘“AH’’ Sheets “MD”’ Drawings QA hh PLP LP P Dn Be O = : . QAA ob o OD02 0) 09 INDEX - MAKE C Camp-On-Busy, 59, 147, 149, 172. Campbell, 3, 55. Catchpole, 10. Charging Batteries, 22. Christus Victor, 161. Alarm Circuits, 88. ‘*All Relay’’ Distributer, 79. ‘*All Relay’’ Driving Ckt., 81. *fAll Relay’’ Searching Ckts., 79. Baer, 33, 50, 55. Tele-Chec, 80. Temperator, 80. BANK - Arcs, 57. Connector Numbering, Multipled, 5, 9, 49. Slip, 49. Strowger, 4, 35, 180. Barry, 4. Counter-Cells, 21. Eliminators, 22. End Cells, 21. Full Float Operation, 22. Voltage Controll, 21. Charg- Bell Laboratories Record, 65. Bell System Technical Journal, 50. Booster Battery Metering, 38. Brown, 3. Bulkley & Durand, 3. Burfeind, 3. BUSY Camp-On, 59, 147, 149, 172. Flash, 58, 137. Over-Ride of, 157, 172. Test, Toll, 61, 138. Tone, 128. Light Pulses, 85. — Operate Time Delay, 84. BATTERY Booster Metering, 38. Controlled Charging, 22. Test, Regular, 37, 107. Heavy Pulses, 85. Impulse Generators, 83. In-And-Out Ckts., 87. Interlocking Relays, 86. Lock-Out Ckts., 86. Lock Pulsing Ckts., 85. Non-Telephone Patents, 88. 12. Voltage Controlled ing, 22. 87. Pulse Cut-In Ckts., 86. Generators, 83. Light & Heavy, 85. Ratio, 83. Repeater Ckts., 84. Shortening Ckts., 84. Stretching Ckts., 85. Release Ckts., 82. © Release Time Delay, 84. Remote Control Ckts., 86. Restoring Ckts., 82. Rotary Interrupter, 77, 92. Sequence Switch, 91. Searching Circuits ‘(All Relay’’, 79. Battery Searching, 78. For Absence of Ground, 77, 92. For Ground, 79. Stepping Switches, 90. Stopping Ckts., 78. Switches ‘‘Around & Return’’, 90. “Unidirectional Rotary’’, 91. “Up, Around & Return’, 91. Local, 56, 106, matic Toll Board. Counter Cells, 21. Counting Relays, 15, 81, 86, 130. Crash Alarm, 174. Crocker, 11. D Clapham, 4, 8, 10, 19, 22, 23, 25, 30, 34, 38, 50, 67, 81. Clare, 45, 67. Clark, 48, 55. Class of Service Tones, 12. Code Call, 12, 13, 165, 171, 173. Code Ringing, 64, 161. Coin Controll, 140. CONDENSER B. P. O. (British Post Office) Bakker, 48. Master Sw. Ckt., 97. Repeater Ckts., 122, 124. Rotary Line Sw. Ckt., 100. Selector Sw. Ckt., 102. Self-Aligning Line Sw. Ckt., Battery Searching, 78. Counting Ckts., 86. 3-Wire, 81, 92. ‘*All Relay’’, 81. Switch, 80. Switch, 35, 36, 45, 57. Connector Sw. Ckt., 105. Finder Sw. Ckt., 111. Complaint Service, 11. Complaint Observation, Composite Dialing, 11. Direction Established, Driving Circuits 2-Wire, 81. a Consecutive Number Service, 56. Conversation Timing, 15, 161. Cord Circuits, 70, 73. Cordless Toll Board - See Auto- - 85. A