230 BELL SYSTEM TECHXICAL JOURNAL 



installation methods in connection with these operations and, in cer- 

 tain cases, the observance of special precautions. For examples, in 

 the operation of twisting to form pairs, triples and quads, it is necessary 

 to avoid appreciable stretching of the conductors, as this would crack 

 and loosen the acetate tilm and impair the appearance of the wire. 

 Fortunately, cracking of the film does not affect the electrical charac- 

 teristics appreciably, so long as it is not severe enough to permit inter- 

 linkage of textile fibers, as discussed in a previous paragraph. 



The first application of cellulose acetate treated wire on a regular 

 production basis was made early in 1930, although considerable quan- 

 tities were installed for service trials in commercial apparatus in 1927. 

 In order to take advantage of the improved electrical characteristics 

 where they are of greatest value, cables and wire used in the toll plant 

 are being changed to employ the new insulation first. Supplementing 

 this program, consideration is being given to extending the use of 

 acetate treated insulation to include wire aggregating annual require- 

 ments of the order of three billion feet for the local plant. Application 

 of the new type wire is being made gradually in order that manufac- 

 turing and installation methods and technique may be further devel- 

 oped as required in connection with this program. 



