The engineer in telephony cannot increase his motive power. A breath against a metal disk changes air waves into electrical currents, and these electrical currents, millions of which are required for a single conversation, must be carried across the continent and produce the same sound waves in San Francisco as were made in New York. Here is a task so fine as to be gigantic. It was to nurse and coax this baby current of electricity 3,000 miles across the continent, under rivers and over mountains, through the blistering heat of the alkali plains and the cold of snow-capped peaks, that has taken the time and thought and labor of the brightest minds of the scientific world.
This great problem in transmission was due to the cumulative effect of improvements, great and small, in telephone, transmitter, line, cable, switchboard and every other piece of apparatus and plant required for the transmission of speech.
The opening of the transcontinental telephone line has been followed by the extension of “extreme distance” transmission into all the states of the Union, by applying these new improvements to the plant of the Bell System. It is now possible to talk from points in any one state to some points in every other state of the Union, while over a very large part of the territory covered by the Bell System, it is possible for any subscriber to talk to any other subscriber, regardless of distance.
During the year 1915 very notable development in radio-telephony, the transmission of speech without wires, was made.
On April 4th the Bell telephone engineers were successful in transmitting speech from a radio station at Montauk Point, on Long Island, to Wilmington, Del.
On the 27th of August, with the Bell apparatus, installed by permission of the Navy Department at the Arlington, Va., radio station, speech was successfully transmitted from Arlington, Va., to the Navy wireless station equipped with Bell apparatus at the Isthmus of Panama.
On September 29th speech was successfully transmitted by wire from the headquarters of the company at 15 Dey Street, New York, to the radio station at Arlington, Va., and thence by radio or wireless telephony across the continent to the radio station at Mare Island Navy Yard, Cal.