Page:Popular Science Monthly Volume 71.djvu/27

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X. Early Aerial Telephone Cables

PROBABLY John I. Sabin was the first telephone man to use an aerial cable. In connecting his line in San Francisco in 1879, he did not run his circuits into a cupola, as was then the fashion, but employed several lengths of a special cable made by Eugene F. Phillips, of Providence. This cable was composed of forty No. 20 soft drawn copper wires, double braided with cotton, then double wrapped in reverse order with rubber paper, the whole being wound with a cotton or jute covering. It cost 20 cents a foot at the factory. It was suspended by using long canvas slings about two feet apart and attached to two heavy iron wires.

In referring to the growth in overhead circuits, Mr. Phillips stated that:

The natural increase in the number of aerial wires created a demand for better insulation and grouping in cables. Hundreds of miles of No. 12 iron wire were braided and dipped in suitable compound for this use. The annoyance from induction soon made a call for anti-induction cable. This want was supplied by a tin-foil cable so called, in which each conductor, after being insulated, was enclosed in a strip of this tin-foil. Cotton-covered wires to the extent of 50 or 100 were cabled together, and after being saturated with paraffine were placed in a lead pipe. This style of aerial cable, although quite satisfactory, has to a great extent been replaced by the paper-insulation underground cable of the present day.

Aerial cables were in use in New York City late in 1879, and before the close of 1880 a total of over 75,000 feet was in use in the city and on the Brooklyn Bridge, principally of ten-conductor capacity. In September, 1880, C. E. Chinnock told the delegates to the first telephone convention:

We have over the East River bridge at the present time, four cables, 3,800 feet long, each cable with seven conductors. These cables have taken the place of cables that were previously there with the ordinary kerite and gutta-percha insulation. In using the cables and talking on one wire, you could hear whatever was said on another wire, and by wrapping each conductor with lead and grounding at intervals, all of the escape and all induction were completely eliminated. These cables have been in use, two of them for six months, and one for nine months, and are now working perfectly.

In May, 1880, W. D. Sargent used a lead-covered aerial cable to connect two exchanges in Philadelphia. This cable was made by David Brooks, Jr., son of the inventor of the Brooks cable. It was