202 THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1957 



sistance, and dielectric strength were then made. These measurements 

 are discussed in detail in a later section of this paper. 



JOINTING OF CORE LENGTHS 



The cable core was manufactured in lengths much shorter than a re- 

 peater section, which necessitated connecting the individual core lengths 

 together. Jointing techniques consisted of brazing the central conductor 

 with a vee-notch type of junction and of molding in a short section of 

 the polyethylene insulation. After silver-soldering the vee-joint, a safety 

 wire consisting of four fine gauge tinned copper wires was bridged across 

 the junction in an open helix and soft soldered at the ends. Extreme care 

 was taken to remove any excess rosin and to eliminate any sharp points 

 on the ends of the safety wires. The safety wire is intended to maintain 

 continuity of the electrical path in case the braze should fail. 



Visual examination of brazes in the actual cable was the only means 

 available for their final inspection. To assure a high degree of quality on 

 these brazes, a system was devised for checking the performance of the 

 operator and the brazing machine initially and at frequent intervals 

 through the use of sample brazes in each of the components, which were 

 tested to destruction. To control the uniformity of brazes, the brazing 

 of the copper wire and tapes was made as automatic as possible by the 

 use of controlled pressure on the components, appropriate sized wafers 

 of silver solder, and an automatically timed heat cycle. The tests on the 

 brazes used to qualify operators and machinery indicated that a high de- 

 gree of braze performance was achieved. 



Pressure and temperature were carefully controlled during the molding 

 of the insulation over the conductor. Periodic checks similar to those 

 described for brazes were made on operator and molding-machine to 

 maintain a satisfactory level of performance. In addition, each molded 

 joint placed in the actual cable was X-rayed and subjected to a high 

 voltage test while immersed in water. 



APPLICATION OF RETURN TAPES AND ARMOR WIRES 



After the core lengths were joined together, they were pulled through 

 the return taping and armoring operations. The machine for applying 

 return tapes was designed specifically for the purpose and was similar in 

 characteristics to the corresponding portion of the strander for the cen- 

 tral conductor. Controlled pay-off tension, automatic breakage detectors, 

 precision guides, and contoured forming rolls to shape the tape, were 

 incorporated in the construction. 



