ELECTRICAL DRYING OF TELEPHONE CABLE 219 



completion of the heating cycle in progress, the operator turns the 

 rheostat to zero voltage and throws a threerway switch, which con- 

 nects the set to the next cable to be heated. 



In preparing the cable for the regular testing process the insulation 

 is removed from one end for a distance of four or five inches, Fig. 8. 

 After the test shows that the cable is satisfactory for lead covering, 

 the insulation is removed from the other end. At each end the wires 

 are bunched together and tied with cotton string so that the individual 

 wires act together in parallel the same as one large wire. The weight 

 of insulation is sufficiently near enough to the ratio of the wire sizes 

 so that a cable made up of several sizes of individual conductors and 

 their particular insulation will heat satisfactorily by applying heat in 

 proportion to the size of wire. 



The electrical drying of cables requires a total of approximately 

 13^ hours as compared to the process it is replacing, which requires 

 12 hours or more and necessitates three-shift operation of the vacuum 

 dryers. The short period permits a more rapid turnover of process 

 stock as well as better planning of manufacture. By coordinating 

 the drying and lead sheathing operations cables are lead covered imme- 

 diately following their removal from the drying tank. The regain 

 of moisture is slight under this condition and therefore the expensive 

 storage oven is unnecessary. As a consequence, the total cost of 

 equipment for the drying operation has been reduced to one-half the 

 former investment value and the floor space from 19,000 square feet 

 to 9500 square feet. Another advantage follows from replacing the 

 continuous three-shift operation by one that operates only in sequence 

 with other operations that may be only on a one- or at most a two- 

 shift basis. 



By applying heat to each conductor in proportion to the size of 

 wire, each cable is given an individual treatment which insures a 

 uniformity of drying not possible in the old vacuum tank process. 

 In the replaced system several truckloads of varying amounts of cable 

 were placed in the same vacuum tank and all dried for the same period. 

 It was an averaging process leading to variations in dryness of indi- 

 vidual cables and followed of necessity from the fact that a large num- 

 ber of different designs and lengths must be handled each day. To 

 approximate individual handling under such a condition, where the 

 drying period was 12 hours or more, would have involved a large 

 number of dryers and increased floor space and operator-time. Also 

 in the replaced system the layers of cable in the center position on 



