SOLDERLESS WRAPPED CONNECTIONS — PART III 



597 



stable and the requirement for intimate contact between wire and ter- 

 minal is considered met. In a typical local talking circuit this amount of 

 resistance variation would correspond to a noise level of approximately 

 — 8 db where db equals 10~^^ watt and where anything less than +26 

 db would give no noise transmission impairment (See Appendix A). 



DEVELOPMENT TEST PROCEDURE — MECHANICAL REQUIREMENTS 



In determining whether a connection meets the General Require- 

 ments 5 and 6, Test Procedure II as follows was devised: 



1. The connection shall be capable of withstanding a stripping force 

 of 3000 grams applied as shown in Fig. 2. 



2. The wire shall be capable of being unwrapped from a terminal 

 without breaking. 



These items are related directly to General Requirements 5 and 6. 

 Experience has shown that under ordinary conditions of handling of 

 connections as cables and frames are wired in the shop, or when a second 

 connection is being made on an already wired terminal, a resistance to 

 stripping in excess of about 3000 grams is required if the demands of 

 General Requirement 5 is to be met. To insure adequate mechanical 

 strength and current carrying capacity, a minimum of six turns is re- 

 quired. If the turns are close wound the strip-off force is readily met. 

 If they are open wound they may strip off with a much lower force. 



When the edge radius R (Fig. 3) of the wrapping tool is too small 

 very high tension can be developed in the wire while wrapping. At very 

 small radii the tension can be sufficient to break the wire. Although 

 wrapping with high tensions in the wire produces a connection which 

 will sustain very high stripping force, the wire is so embrittled that 



WALL THICKNESS 



Fig. 3 



WRAPPING SPINDLE 

 TERMINAL HOLE 



Solderless connection wrapping tool. 



