NEW GENER.\L PURPOSE RELAY 1027 



cost reduction of the relay. It became evident that the development of 

 new manufacturing methods as well as new tlesigns were essential in 

 leaching the ambitious objectives. For these reasons, the manufacturing 

 engineers of the Western Electric Company were actix'e pailicipants in 

 the development of the new relay from the beginning. 



Many new forms of relay designs were considered and studied includ- 

 ing such tj'pes as miniature, magnetic contact, piezoelectric, etc. As a 

 result, one general form, first proposed by H. C. Harrison, gave the most 

 promise of meeting the manifold requirements. This is the wire spring 

 type characterized by the wire spring subassemblies with code card oper- 

 ation of pretensioned, low stiffness springs. Actually, the general form 

 of the wire spring relaj' proposed by IMr. Harrison constitutes an entire 

 new class of relaj-s with many possible variations. These include various 

 t^'pes of code card operation and various forms of contact operation, 

 operated by any of a number of magnet structiu'es. 



The new class of relays has the following important advantages: 



1 . Pretensioned, low stiffness ^vire springs make possible (a) assembly 

 to give close control of contact force without individual spring adjust- 

 ment; and (b) essentially constant contact force thi'oughout the life of 

 the relay and its contacts. 



2. Wire spring subassemblies make possible (a) favorable manufacture 

 of a multiplicity of contact springs by molding; (b) lower assembly costs 

 because fewer piece parts are needed; and (c) simple code card operation. 



3. Code card operation makes possible (a) standardized and simple 

 assembly; (b) accurate control of contact position; (c) essential elimina- 

 tion of locked contacts ; (d) complete independence of twin contacts ; and 

 (e) simple means for pro\'iding a large number of contact combinations. 



A continuous and comprehensive study was necessary of the char- 

 acteristics and probable manufacturing costs of many forms of the wire 

 spring relay famil3^ As a result, after passing through se\'eral major 

 designs, the basic design of the present relay was adopted. H. M. Knapp 

 and C. F. Spahn proposed important features of this design. This form 

 represented advantages over other types in 



1. reducing the number and amount of dimensional variations con- 

 trolling the contact gaps. In turn, this made possible smaller armature 

 movement, shorter operating and release times and less chatter of the 

 contacts ; 



2. reducing the number of code cards required to provide the large 

 number of contact combinations needed in switching systems; 



3. reducing the manufacturing and wiring costs; 



4. increasing the mechanical life. 



