Coaxial Debut

In ordinary telephone communication, the voice is converted into electrical impulses which travel over a wire, are transformed into sounds again at the receiving end. In radio-telephony--as between the shore and a ship at sea, for example--the voice is converted into waves of radiation which travel through the air. But weaves of radiation at radio frequencies can also be guided along a cable, if the stations are fixed arid if the cable can carry a wide enough frequency band. Such an arrange ment enables the cable-carried waves to be fortified by amplifiers at intervals along the route, minimizes tonal losses due to static and fading. Such a cable is the famed coaxial cable developed by American Telephone & Telegraph Co.'s research subsidiary, Bell Telephone Laboratories.

Dr. Frank Baldwin Jewett, Bell Telephone's president, proudly explained in Manhattan last week that for radiotelephony between fixed points, Bell's coaxial cable provides "a piece of the ether which has been segregated from all the other ether in the world." Because it can carry a frequency band 1,000,000 cycles wide and can "pipe" tele vision underground for hundreds of miles.

the Bell cable first made a name for itself as a television possibility. This led to a hue & cry of Monopoly! when the company asked the Federal Communications Commission for permission to install an experimental pipeline between Manhattan and Philadelphia. The company explained that its primary interest in the cable was for telephone communication, that it had no television projects afoot, but would lease the cable to all reputable television experimenters without favor. The Commission thereupon withdrew its objections and installation of the Manhattan-Philadelphia line was started (TIME, Oct. 14, et seq.). Last week, with installation complete, A. T. & T. summoned newshawks to its downtown Manhattan offices for the cable's first public demonstration. The cable can transmit 240 telephone messages at once. The voices are reduced to radio frequencies and all poured on the cable at once, separated at the receiving end by quartz crystal wave filters. Last week an engineer in one room merely talked to a reporter in the adjoining room, but between speaker and hearer the message made 40 trips between Manhattan and Philadelphia (3,800 miles), the frequency being shifted to a different wave length after every round trip. Then 20 frequencies were poured on the cable at once-- which taxed only one-twelfth of its maximum capacity. Even when voices were lowered almost to a whisper, practically no distortion was noticed.

"It is strange," said Dr. Jewett, "how you can take a voice to pieces, mess it all up, and still get something you can understand." Dr. Jewett has been careful to keep the cable's development anonymous, to credit many workers with research contributions.

This excellent conduit consists essentially of two copper tubes with copper wires running through the centre of each, the whole sheathed in lead. The current travels on the inside wall of the tubes, the outside skin of the wires. Whereas ordinary telephone trunk lines have booster stations at least every 50 miles, serviced by human attendants, the coaxial cable has automatic booster stations every ten miles, accessible through manholes if repairs are needed.

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