1026 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1952 



U and Y type relays but with substantially lower manufacturing costs. 

 As the development of the relay proceeded, it became possible to expand 

 the requirements without appreciably altering the expected relay cost. 

 In particular, it became possible to design the new relay to operate and 

 release faster or to use less electrical power, to operate more often before 

 appreciable wear occurred, etc. The improved performance character- 

 istics of the AF Avdre spring relay, as described later, are of equal eco- 

 nomic importance to those associated with lower manufacturing cost. 

 The broad requirements were reduced to the following design objec- 

 tives: 



1. Lower cost — 50 per cent of U type relaJ^ 



2. Reduced operating electrical power. 



3. Faster operate and release times. 



4. Long life — one billion operations. 



5. Improved contact performance. 



These broad design objectives do not specifically state a large number 

 of other characteristics which must be at least as favorable as those of 

 the U and Y relay family. This refers to such items as: space rec^uired, 

 magnetic interference, wiring costs, contact combinations, field servicing 

 and repairs. 



3. DESIGN POSSIBILITIES 



The studies of new relay design possibilities started with a careful 

 review of the U type relay experience. In fact, much of the early thinking- 

 considered various modifications of U type and other existing relays. In 

 general, these studies indicated that about half of the manufacturing 

 cost of U type relays came from assembly and adjusting operations. 

 Accordingly, these operations required major revision for a substantial 



CONTACT 

 COVER 



STATIONARY 

 WIRE ASSEMBLY 



TWIN WIRE ASSEMBLY 



^FOR MAKES 



/ /FOR BREAKS 



— MOUNTING NUT 



CORE 



ARMATURE AND 

 HINGE SPRING 



MOUNTING 

 BRACKET 



^COIL CLAMP 



Fig. 3 — Top view of the relay, showing location of parts 



