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BELL SYSTEM TECHNICAL JOURNAL 



ends are sealed and the cable is prepared for shipment. Certain 

 types of cable receive an additional gas pressure test to detect minor 

 defects in the lead sheath which otherwise may have escaped attention. 

 Dry nitrogen is forced into the cable to a predetermined pressure and 

 the cable is allowed to stand for a specified period. Loss of pressure 

 during the test period indicates that the sheath or seals contain one or 

 more defects. 



Armoring of Telephone Cable 



Two types of armored telephone cal)le are in use, Fig. 38. Subma- 

 rine telephone cables for ri\'ers and harbors are usually protected by 



TAPE ARMORED CABLE 



SUBMARINE CABLE 

 Fig. 38 — Typical construction of tape and wire armored cables. 



layers of jute and wire placed on the outside of the lead sheath. 

 This type of armor is quite familiar and is called wire armoring. 

 Cable buried in a dirt trench is armored in a similar way except the 

 wire is replaced by two layers of steel tape. This is called tape 

 armoring. It is adapted to certain localities where there are long 

 stretches of open country and the conditions indicate one or two cables 

 will handle the requirements for a considerable number of years. 



A typical wire armor is made up of a bedding of 100 or 150 pound 

 jute roving, impregnated with suitable preservative after serving, by 

 passage through immersion troughs, over which a layer of armor wires 

 is applied. In some cases, a covering of outer jute flooded with coal tar 

 is used. When an unusual degree of protection is desired, a second 

 layer of armor wire is applied. In such cases a bedding of jute is used 

 between the layers. 



Recent trends in the design of wire armored cables are leading 

 toward cables of nmch larger diameter. At the Point Breeze plant 

 there is an unusually large wire armoring machine (Fig. 39). It is 

 designed to handle cable up to 5% inches in diameter over the armor. 



