An Experimental Electronically Controlled 

 Antomatic Switching System 



By W. A. MALTllANKR AND H. IvARLE VAUGHAN 



(Manuscript received February 15, 1952) 



An automatic telephone switching system, built as a laboratory experiment, 

 is described in which electronic techniques, high speed relays and a sub- 

 scriber telephone with a preset dialing mechanism were employed. One-at-a- 

 time operation within the office was made possible by these fast tools; that 

 is, only a single control circuit was provided for each function. This ex- 

 perimental system, although not commercially economical, showed that an 

 advantageous reduction in the number of control and connector circuits is 

 made possible by this method of operation. 



IXTRODUCTIOX 



This paper describes a laboratory experiment in automatic telephone 

 switching systems. The in\'estigation was conducted at the research 

 level to gather valuable information and circuit techniques from a labo- 

 ratory trial and not to evolve a system economically competitive with 

 existing systems since the area of investigation is always broader and 

 the results more general in character when the work is imfettered 

 by economic restraints. Indeed, the results are not economically com- 

 petitive. 



Purposes of the investigation were to determine what advantages may 

 be derived from faster operation, largely through the use of electronic 

 technicjues, and to introduce and test some previously imexplored philos- 

 ophies in switching and signaling. Some of the basic tools employed were 

 dry-reed relays, mercury relays, multi-element cold cathode gas tubes, 

 cold cathode gas diodes, and thermionic electron tubes. An experimental 

 subscriber's telephone set, incorpoi'atiiig a preset dial mechani.sm with 

 circuits for generating dialing signals of a new form, together with 

 suitable signal receivers for the central office was designed as well as a 

 novel type of switching network with its control circuits. A basic aim 

 of the experiment was one-at-a-time operation within the central office. 



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