724 THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1951 



aerial cable jobs. Certain differences also were necessary in the mounting 

 details. These various differences were recognized in the case code designa- 

 tions. 



Beginning in the early 1930's, sections of lead sleeving with soldered lead 

 (and later on, brass) tops and bottoms came into general use for small load- 

 ing complements. To add mechanical support to the inherently weak, cylin- 

 drical lead sleeve, the larger-size lead cases were equipped with inner-lining 

 steel tubes when used on cables maintained under gas pressure. The lead 

 cases^"^ are less expensive than rectangular-shaped welded-steel designs of 

 equivalent potting capacity, and are suitable for use on underground and 

 on aerial cables. On the lead cases used in buried cable projects, and on their 



W 





Fig. 21 — Si)lice loading cases for exchange area loading. 88 mh coils potted 

 in cardboard containers, and equipped with fabric tapes for fastening 

 to cable core at splice. At left: 622 coil. At right: 632 coil. 



stub cable sheaths, a special finish reinforced with armor provided protec- 

 tion against injury by rodents. Corresponding protection was also provided 

 on the sheaths of stub cables of cast iron and welded steel cases intended 

 for use on buried cables. 



Another general change in the design of loading coil cases started about 

 1940 with the introduction of cylindrical, J-inch steel-tubing in place of thick 

 steel-plate rectangular designs. ^^^ While initially this was a steel conserva- 

 tion measure, it was found to be very advantageous with respect to manu- 

 facturing techniques and economy. This development will eventually reduce 

 the use of the previously mentioned lead-sleeve designs. 



The basic problem of securing the most economical designs for different 

 potting complements and different installation conditions has included the 

 provision of special case designs for placement in cable splices, which do not 



<"^ Some lead sleeve cases for exchange area loading are shown in Fig. 17 (page 467). 

 ^"^ Some of these cylindrical thin steel cases are shown in Fig. 18 (page 468) and in the in- 

 stallation photographs Figs 26, 27, 28 A and 28B (pages 728, 729, 730 and 731 , respectively). 



