158 BELL SYSTEM TECHNICAL JOURNAL 



coaxial cables will provide for broad-band transmission service such as is 

 required for television. 



A cable is now being installed between Terre Haute and St. Louis which 

 contains six coaxial tubes to provide telephone circuits, and which may, 

 in the future, find use in connection with the provision of intercity television 

 networks. 



The structure of the tubes used with coaxial cables consists of a central 

 copper conductor within a copper tube about \ in. in diameter, made from 

 flat copper strip which is formed around the insulating discs. Around each 

 copper tube are two steel tapes which supplement the shielding of the copper 

 tube in preventing interference between tubes in close proximity. The cen- 

 tral conductor is separated from the outer conductor by slotted insulating 

 disks which are forced onto the wire. The cables are formed with an appro- 

 priate number of these tubes along with some small gauge pairs used for 

 control and operating purposes. 



In the case of underground cables buried directly in the earth, jute or plas- 

 tic protective coverings are used to assist in reducing sheath corrosion. 

 In some parts of the country it is essential to add a metal covering outside 

 the lead sheath and the plastic or jute to protect the cables against the 

 operations of ground squirrels or pocket gophers. In certain areas these 

 animals have been found to carry away long sections of the jute covering 

 and will chew holes in the lead sheath unless other metal protection is pro- 

 vided. Copper is sometimes used for this metal covering to assist in light- 

 ning protection. 



Repeaters in the coaxial system are now located at intervals of about five 

 miles. Power for repeaters in the auxiliary stations is supplied from the 

 adjacent main stations located at something over 50 miles at 60 cycles over 

 the coaxial conductors thernselves. 



Coaxial cables are in regular operation between New York and Philadel- 

 phia and between Minneapolis and Stevens Point, Wisconsin, a total dis- 

 tance of nearly 300 miles. A network of such cables totaling about 7,000 

 route miles and including a second transcontinental cable route is being 

 planned over additional routes. The requirements of the armed forces, 

 general business conditions, the volume and distribution of long distance 

 telephone messages, the availability of the necessary manufactured cable 

 and equipment, and other factors may modify the extent of this construc- 

 tion, the time of starting, and the routes which will be undertaken. 



Western Electric Recording System — U. S. Naval Photographic Science 

 Laboratory} R. 0. Strock and E. A. Dickixsox. This paper describes 

 the complete 35-mm film and ?)i\ or 78 rpm. disk recording and re-recording 

 equipment installed for the U. S. Navy at the Photographic Science Labora- 

 tory, Anacostia, D. C. Modern design, excellent performance, and ease of 

 operation are features of the installation. 



' Jour. Soc. Motion Picture Engineers, December 1944. 



