Technical Developments Underlying the Toll Services of 



the Bell System 



T.MJI.i; Ol' CONTKNTS 



F'age 

 Early Developments 



General— Telephone I iist ruments 2 



Telephone Switching Systems 4 



Telephone Circuits and Cables 5 



Early Toll Service 6 



The Phantom Circuit 9 



Superposed Telegraph on Telephone Circuits 10 



Development of Mathematical Theory of Transmission — Loading 13 



I nterurban Toll Cables 14 



Possibilities and Problems Associated with the Use of the Telephone Repeater . 15 



Toll Cable vSystem 22 



Time Factor in Telephone Transmission 26 



Multi-Channel Telephone Systems 30 



Associated Technical Developments 34 



Regulators 34 



Equalizers 36 



Signaling Systems 37 



Telegraph System 38 



Auxiliary Apparatus and Equipment 39 



Development of Methods of Measurement and Maintenance for Toll Circuits. . 39 



Special Services — Program Transmission 43 



Telephotography 46 



Other Special Services 46 



Toll Operating Methods 46 



Operating Method Defined 46 



Interrelation of Method and Equipment Design 47 



Rearrangement of Plant Brought about by Changes in Method 47 



Trunking Methods Distinguished from Operating Methods 48 



Description of Trunking Methods — 48 



Call-Circuit Trunking Method 48 



Straightforward Trunking Method 49 



Ringdown Trunking Method 49 



Dial Trunking Method 49 



Description of Toll Operating Methods 50 



General Characteristics of Toll Calls and Operating Methods 50 



A-Board Toll Operating Method 51 



Two-Number Toll Operating Method 52 



Two-Ticket Toll Operating Method 52 



Single-Ticket Operating Method 54 



Combined Line and Recording (CLR) Method 54 



Evolution of Toll Operating Methods 57 



General Toll Switching Plan 58 



The Joint Occupancy of Plant 65 



Rental Arrangements 66 



Joint Maintenance Arrangements 68 



General 69 



Standardization 69 



Plant Design 70 



Construction, Maintenance, and Operation 71 



General 71 



Bibliography 72 



1 



