FLEXIBLE REPEATER DESIGN 93 



central conductor and the outer conductor, or container, are capable of 

 becoming electrically conducting paths if filled with water vapor. As 

 pointed out in companion papers,^' ^ the voltage between the repeater 

 (and cable) central and outer conductors is in the neighborhood of 2,000 

 volts at the ends of the transatlantic system. 



The filling of the seal interspace with a liquid would defeat one func- 

 tion of the rubber seal if special features were not provided in the rubber 

 seal design. Very slight displacement of the rubber seal toward the glass 

 seal because of sea pressure, or resulting from reduction in volume owing 

 to falling temperature, would otherwise build up pressure in the liquid 

 and on the glass seal. We avoid this by providing a kind of resihence in 

 the interspace chamber. Three small brass bellows, partly compressed, 

 occupy fixed cavities in the chamber. They can compress readily and 

 maintain essentially constant conditions independent of external pres- 

 sures and temperatures. 



The entire repeater assembly enclosed in copper is approximately 23 

 feet long. Tails of cable at each end make the total length about 80 feet 

 before splicing. The central conductor of each cable tail is joined to the 

 rubber seal central conductor, with the insulation molded in place in 

 generally the same manner as in cable-to-cable junctions elsewhere in 

 the system. The outer-conductor copper tapes of the cable tails are 

 electrically connected to the copper core tubes. 



The copper region is coated with asphalt varnish and gutta percha 

 tape to minimize corrosion. Over this coating bandage-Hke layers of 

 glass fabric tape are built up to produce an outer contour tapering from 

 cable diameter at one end up to repeater diameter and back down to 

 cable diameter at the opposite end. The tape covering is saturated with 

 asphalt varnish. This tape is primarily a bedding for the armor wires 

 that are laid on the outside of both cable tails and repeater to make the 

 repeater cable-like in its tensile properties and capable of being spliced 

 to cable. 



In the region of the repeater proper where the diameter is double that 

 of cable, extra armor wires are added to produce a layer without spaces. 

 Also, to avoid subjecting the repeater to the torque characteristically 

 present in cable under the tensions of laying, a second layer of armor 

 wires of opposite lay is added over the first layer. This armoring process 

 is so closely related to the armoring of cable core in a cable factory that 

 it is performed there. 



Materials 



Following the same design philosophy applied to the repeater compo- 

 nents, the materials of construction of the repeater container and seals 



