4 BELL SYSTEM TECHNICAL JOURNAL 



and the wire advances from 175 to 200 feet per minute depending on 

 the length of wrap. 



From a process standpoint manila paper was selected originally 

 because of its strength and elasticity and in the development of 

 equipment to serve it full advantage was taken of these two charac- 

 teristics, particularly for the insulation of the finer gauges of wire. 

 This fact tended to handicap the adaptation of cheaper papers to this 

 purpose when the changing conditions in the paper industry made such 

 a step desirable, since the readily available substitutes were some- 

 what inferior in these two respects. Studies were undertaken to 

 modify the equipment for serving ribbon paper with the idea of 

 adapting it for handling this paper, but with only indifferent success. 

 The mixing of varying amounts of wood pulp with manila stock proved 

 to be a successful solution in the case of heavier papers, but in the 

 thinner ones the results were not satisfactory, and progress in this 

 direction was at a standstill. 



Fig. 2 — General view of pulp insulating equipment. Take-up and dryer in left 

 foreground, polishers and wet machine in right center and wire supply and pulp 

 preparation equipment in right and background. 



The Development of Pulp Insulated Wire 



In line with the generally recognized need for a radical change in 

 the insulating situation some work was initiated in 1921, with the idea 

 of determining the possibilities of producing a continuous homogeneous 

 paper covering directly on the wire and a scheme was worked out which 



