592 THE BELL SYSTEM TECHNICAL JOURNAL, MAY 1953 



life (forty years) because of corrosion or because of relaxation of the 

 internal stresses in the wire or terminal. 



4. The sum of the areas of intimate contact should be equal to or 

 larger than the cross-section of the wire to prevent local heating. 



5. The connection should be mechanically stable so that forces applied 

 to the connection during shipment, installation and subsequent main- 

 tenance activities will not dislodge the wire and break the points of 

 intimate contact. 



6. The wire should not be embrittled during the wrapping operation 

 so that it will subsequently break due to vibration, handling, or un- 

 wrapping. 



TRANSLATION OF GENERAL REQUIREMENTS INTO TEST REQUIREMENTS 



In order to evaluate the feasibility of solderless wrapped connections, 

 extensive development studies were necessary so that a good estimate 

 could be obtained as to whether these connections would meet these 

 general requirements under a wide variety of conditions and with suffi- 

 cient margin to provide for ease of manufacture. It was necessary to 

 translate these requirements first into a set of development test require- 

 ments and second into a set of shop inspection requirements. These two 

 translations of requirements will not necessarily be the same although 

 there will be a large degree of overlap. In either translation they can be 

 broken down into two distinct areas. These two areas of tests cover 

 those tests which are related to evaluating (1) life and electrical stability 

 of the connection and (2) mechanical stability. 



A great deal of engineering judgment was used in the translation of 

 the physical requirements into inspection requirements and this judg- 

 ment took into account the special nature of conditions to be encountered 

 in telephone offices. Consideration was given to the methods of handling 

 the wire, the manipulations of installation and maintenance men when 

 working on central office equipment, the effect of vibration, the effect of 

 variation in tool dimensions and the like. Furthermore, a good deal of 

 knowledge of the corrosion and relaxation process had to be developed 

 before it could be judged on the basis of accelerated tests that the con- 

 nections might be expected to have a satisfactory field life. 



There may be applications where the translation of the physical re- 

 quirements into test requirements may be different, perhaps quite 

 different, from the translation made for the telephone apparatus which 

 was in mind during this investigation. The use of other kinds and sizes 

 of wire or terminals may require an evaluation quite different from the 

 one presented here. Nevertheless, the test requirements herein estab- 



