A NEW TYPE OF UNDERGROUND TELEPHONE WIRE 



449 



Fig. 2 — \'ulcanizer for buried wire splice. The buried wire is in the center and 

 storage battery leads for heating vulcanizer are above and. below on right. 



mission requirements to be placed on a buried circuit will, of course, 

 depend upon the facilities with which it is associated, it is expected 

 that buried circuits up to about five miles in length will, in general, not 

 require loading. Where loading is required, provision has been made 

 for it in the form of a permalloy dust ^ core coil having -14 millihenries 

 inductance which is individually potted with rubber insulated lead- 

 out wires. It is intended to be spliced into the wire at 8,000-foot 

 intervals and buried directly in the ground with the wire. 



The potting arrangement for the buried wire coil has several features 

 of interest. The loading coil is first potted in a small metal container 

 which is vacuum impregnated with a moisture resistant compound. 

 The lead-out wires from this container are then spliced to stub lengths 

 of the buried wire, as shown in Fig. 3. This container is then placed 

 in a larger sheet copper container, the rubber insulated wires being 

 brought out through tubes soldered into the copper container and 

 pressed down into intimate contact with the rubber insulation. The 

 lead-out wires are taped for reinforcement at the outer ends of the 



^ G. W. Elmen, Bell System Technical Journal, Volume 15 (January 1936). 



