1112 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1954 



Fig. 1 — New 30-contact relay with contact cover detached. 



This development also includes two modifications of the new wire 

 spring relay for replacement use and for additions in existing crossbar 

 equipments. They are 60-contact pair relays, each consisting of two 

 30-contact units attached to a common mounting bracket. They are 

 completely interchangeable with existing crossbar system multicontact 

 relays. When a new improved relay is developed, it is almost invariably 

 necessary to continue in manufacture and carry in merchandise stock, 

 small demand codes of the old relays for many years. In this case, how- 

 ever, manufacture of the old multicontact relays will be discontinued 

 and all future needs will be supplied by the new product. 



OBJECTIVES AND REQUIREMENTS 



At the start of the project, all requirements from the standpoint of 

 operating performance, circuit design and equipment use, were prepared 

 in detailed form. The principal design objectives are summarized as 

 follows : 



Electrical and Mechanical 



1. Operate and release times as fast as economically possible. 



2. Forty year life, or 200 million operations, with no adjustment 

 necessary during the first 100 million operations. 



