226 BELL SYSTEM TECHNICAL JOURNAL 



which are securely fastened to the mounting plate by means of metal 

 eyelets. The armature "B" is hinged at the rear by the use of a thin, 

 steel reed, securely riveted to the armature. The switching arrange- 

 ments which the armature controls arc in the form of nickel siKer 

 springs "C" with thfc contacts "D", at the front and in i)lain \ii\v. 



Fig. 13 



^EkL- 



Fig. 14 



The springs and contacts are mountetl vertically which is particularly 

 effective in keeping the contacts clean. The contact points are made 

 from platinum or a recognized equivalent, and are designed in the 

 form of points and discs to facilitate alignment and adjustment. 

 Two designs of contacts have been standardized; one size being 

 used for the customary electric currents and wear conditions en- 

 countered in manually operated systems and a larger size for the 

 somewhat more severe conditions of wear frequently encountered in 

 automatic systems. All contacts are electro-welded on their respective 

 spring supports and the two sizes are shown in Fig. 13 and Fig. 14, 

 respectively. 



The springs and their associated contacts are designed in twenty- 

 six switching arrangements as shown in Fig. 1. A single relay may 

 be provided with one of these switching arrangements or any one of 

 these twenty-six arrangements may be paired with any other arrange- 

 ment. Thus on a single relay there may be chosen any one of 377 

 switching or contacting combinations. The 377 spring combina- 

 tions provide a great flexibility in circuit design and permit of uniform 

 and efficient equipment layouts. 



In manufacturing the rela\s the spring asseml)lies are clamped 

 together under high compression before tightening the screws which 

 hold them together. This insures that the s|)rings retain their posi- 

 tion and adjustment throughout a long period of time. The arrangement 

 of the springs is such that definite stops or sui)ports are provided 

 for each spring either on the front spool head or on the armature. 

 In tensioning or adjusting the relay springs against their supports, 



