THE BELL SYSTEM 



TECHNICAL JOURNAL 



VOLUME XXXI NOVEMBER 1952 number6 



Copyright, 1952, American Tele-phone and Telegraph Company 



A New General Purpose Relay for 

 Telephone Switching Systems 



By ARTHUR C. KELLER 



(Manuscript received July 14, 1952) 



This paper describes a new general purpose electromagnetic relay for use in 

 telephone switching systems. It is a wire spring relay known as the AF type 

 relay and, with variations which provide slow release or marginal char- 

 acteristics, it is known as the AG and AJ relay, respectively. Fig. 1 shows a 

 typical AF type relay. Fig. 2 shows all of the parts of the relay and Fig. 3 

 is a drawing showing the relay assembly. 



1. BACKGROUND 



The general purpose relay is one of the most important components of 

 telephone switching systems.^ These relays constitute the most repetitive 

 buiUUng block in switching equipment. Since several million are produced 

 annually, low manufacturing cost is extremely desirable. Also of prime 

 importance are low operating and maintenance costs. General purpose 

 relays are, therefore, under constant observation and study by the tele- 

 phone operating companies as the users, by the Western Electric Com- 

 pany as the manufacturer, and by Bell Telephone Laboratories as the 

 designer. The AF wire spring relay and its variations are the result of 

 such studies. 



A general purpose relay for telephone switching sj^stems must meet 

 a large number of diverse requirements. It must be capable of being 

 assembled with any one of a variety of magnet coils having a wide range 



1 S. P. Shackleton and H. W. Purcell, "Relays in the Bell System", Bell System 

 Tech. J., Jan., 1924, p. 1. 



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