Abstracts of Technical Articles from Bell System Sources 



The Manufacture of Ruhher- Covered Wires for Telephone Installa- 

 tions.^ S. E. Brillhart. Rubber-insulated wires are extensively 

 used by the telephone companies in connecting up apparatus and 

 equipment which is exposed to varying climatic conditions in the same 

 fashion in which rubber-covered wires are employed by other electrical 

 industries. In order to meet all size, strength, and electrical require- 

 ments the various wires available for use must differ widely from one 

 another and from commercial rubber-insulated wires, in the character 

 of insulation with which they are covered, as well as the properties of 

 the conductors. 



At one extreme this diverse group includes wires for such use as 

 telephone drops which extend from the cable terminals to the buildings 

 in which the stations are located. These drop wires must be capable 

 of carrying heavy snow and ice loads in winter and also be able to 

 withstand exposure to summer heat and strong sunlight in hot climates. 

 They are Nos. 14 and 17 B. & S. gauge hard-drawn copper and bronze 

 conductors with insulations of relatively high quality containing more 

 than 30 per cent of rubber and covered with a w^eatherproofed cotton 

 braid. At the other end the group contains wires for connecting up 

 instruments within buildings. Being supported frequently and pro- 

 tected from exposure, they are made from No. 22 gauge conductors, 

 insulated with a thinner w^all and covered with a colored glazed cotton 

 braid. 



A plant is located at the Point Breeze Works, Baltimore, in which 

 certain unique methods and departures from conventional methods 

 of manufacturing rubber-covered wires have been reduced to practice 

 on a large scale. This paper purposes to describe the plant. 



Some Recent Developments in Underground Conduit Construction in 

 the Bell System."^ A. L. Fox. In the past the type of joint made by 

 trowelling cement mortar around the abutting ends of multiple clay 

 conduit has not been entirely satisfactory because in some cases it 

 permitted infiltration of sand and silt which obstructed the ducts. 



\'arious types of joints have been investigated, including a modified 



1 Mech. Engg., June, 1932. 



2 Bell Telephone Quarterly, July, 1932. 



622 



