The Telephone, Motograph, And Microphone - 7

The Telephone, Motograph, And Microphone - 7

By March, 1881, there were in the United States only nine cities of more than ten
thousand inhabitants, and only one of more than fifteen thousand, without a telephone
exchange. The industry thrived under competition, and the absence of it now had a
decided effect in checking growth; for when the Bell patent expired in 1893, the total of
telephone sets in operation in the United States was only 291,253. To quote from an
official Bell statement:
"The brief but vigorous Western Union competition was a kind of blessing in disguise.
The very fact that two distinct interests were actively engaged in the work of organizing
and establishing competing telephone exchanges all over the country, greatly facilitated
the spread of the idea and the growth of the business, and familiarized the people with the
use of the telephone as a business agency; while the keenness of the competition,
extending to the agents and employees of both companies, brought about a swift but quite
unforeseen and unlooked- for expansion in the individual exchanges of the larger cities,
and a corresponding advance in their importance, value, and usefulness."
The truth of this was immediately shown in 1894, after the Bell patents had expired, by
the tremendous outburst of new competitive activity, in "independent" country systems
and toll lines through sparsely settled districts--work for which the Edison apparatus and
methods were peculiarly adapted, yet against which the influence of the Edison patent
was invoked. The data secured by the United States Census Office in 1902 showed that
the whole industry had made gigantic leaps in eight years, and had 2,371,044 telephone
stations in service, of which 1,053,866 were wholly or nominally independent of the Bell.
By 1907 an even more notable increase was shown, and the Census figures for that year
included no fewer than 6,118,578 stations, of which 1,986,575 were "independent."
These six million instruments every single set employing the principle of the carbon
transmitter--were grouped into 15,527 public exchanges, in the very manner predicted by
Bell thirty years before, and they gave service in the shape of over eleven billions of
talks. The outstanding capitalized value of the plant was $814,616,004, the income for
the year was nearly $185,000,000, and the people employed were 140,000. If Edison had
done nothing else, his share in the creation of such an industry would have entitled him to
a high place among inventors.
This chapter is of necessity brief in its reference to many extremely interesting points and
details; and to some readers it may seem incomplete in its references to the work of other
men than Edison, whose influence on telephony as an art has also been con- siderable. In
reply to this pertinent criticism, it may be pointed out that this is a life of Edison, and not
of any one else; and that even the discussion of his achievements alone in these various
fields requires more space than the authors have at their disposal. The attempt has been
made, however, to indicate the course of events and deal fairly with the facts. The
controversy that once waged with great excitement over the invention of the microphone,
but has long since died away, is suggestive of the difficulties involved in trying to do
justice to everybody. A standard history describes the microphone thus:
"A form of apparatus produced during the early days of the telephone by Professor
Hughes, of England, for the purpose of rendering faint, indistinct sounds distinctly
audible, depended for its operation on the changes that result in the resistance of loose
contacts. This apparatus was called the microphone, and was in reality but one of the
many forms that it is possible to give to the telephone transmitter. For example, the
Edison granular transmitter was a variety of microphone, as was also Edison's
transmitter, in which the solid button of carbon was employed. Indeed, even the platinum
point, which in the early form of the Reis transmitter pressed against the platinum contact
cemented to the centre of the diaphragm, was a microphone."
At a time when most people were amazed at the idea of hearing, with the aid of a
"microphone," a fly walk at a distance of many miles, the priority of invention of such a
device was hotly disputed. Yet without desiring to take anything from the credit of the
brilliant American, Hughes, whose telegraphic apparatus is still in use all over Europe, it
may be pointed out that this passage gives Edison the attribution of at least two original
forms of which those suggested by Hughes were mere variations and modifications. With
regard to this matter, Mr. Edison himself remarks: "After I sent one of my men over to
London especially, to show Preece the carbon transmitter, and where Hughes first saw it,
and heard it--then within a month he came out with the microphone, without any
acknowledgment whatever. Published dates will show that Hughes came along after me."
There have been other ways also in which Edison has utilized the peculiar property that
carbon possesses of altering its resistance to the passage of current, according to the
pressure to which it is subjected, whether at the surface, or through closer union of the
mass. A loose road with a few inches of dust or pebbles on it offers appreciable resistance
to the wheels of vehicles travelling over it; but if the surface is kept hard and smooth the
effect is quite different. In the same way carbon, whether solid or in the shape of finely
divided powder, offers a high resistance to the passage of electricity; but if the carbon is
squeezed together the conditions change, with less resistance to electricity in the circuit.
For his quadruplex system, Mr. Edison utilized this fact in the construction of a rheostat
or resistance box. It consists of a series of silk disks saturated with a sizing of plumbago
and well dried. The disks are compressed by means of an adjustable screw; and in this
manner the resistance of a circuit can be varied over a wide range.
In like manner Edison developed a "pressure" or carbon relay, adapted to the transference
of signals of variable strength from one circuit to another. An ordinary relay consists of
an electromagnet inserted in the main line for telegraphing, which brings a local battery
and sounder circuit into play, reproducing in the local circuit the signals sent over the
main line. The relay is adjusted to the weaker currents likely to be received, but the
signals reproduced on the sounder by the agency of the relay are, of course, all of equal
strength, as they depend upon the local battery, which has only this steady work to
perform. In cases where it is desirable to reproduce the signals in the local circuit with the
same variations in strength as they are received by the relay, the Edison carbon pressure
relay does the work. The poles of the electromagnet in the local circuit are hollowed out
and filled up with carbon disks or powdered plumbago. The armature and the carbontipped
poles of the electromagnet form part of the local circuit; and if the relay is actuated
by a weak current the armature will be attracted but feebly. The carbon being only
slightly compressed will offer considerable resistance to the flow of current from the
local battery, and therefore the signal on the local sounder will be weak. If, on the
contrary, the incoming current on the main line be strong, the armature will be strongly
attracted, the carbon will be sharply compressed, the resistance in the local circuit will be
proportionately lowered, and the signal heard on the local sounder will be a loud one.
Thus it will be seen, by another clever juggle with the willing agent, carbon, for which he
has found so many duties, Edison is able to transfer or transmit exactly, to the local
circuit, the main-line current in all its minutest variations.