TELEPHONY.
In the foregoing chapters I have described
the method of transmitting musical tones telegraphically
and its applications to multiple telegraphy, as well
as to a mode of communicating with a moving railroad-train.
As I stated in a former chapter, after discovering
a method of transmitting harmony as well as melody,
I had in mind two lines of development, one in the
direction of multiple telegraphy, and the other that
of the transmission of articulate speech. I will
not attempt to give the names of all the people who
have contributed to the development of the telephone
(as this alone would fill a volume) but only describe
my own share in the work leaving history
to give each one due credit for his part. While
I do not intend, here, to enter into any controversy
regarding the priority of the invention of the telephone,
I wish to say that from the time I began my researches,
in the winter of 1873-4, until some time after I had
filed my specification for a speaking or articulating
telephone, in the winter of 1875-76, I had no idea
that any one else had done or was doing anything in
this direction. I wish to say further that if
I had filed my description of a telephone as an application
for a patent instead of as a caveat, and had prosecuted
it to a patent, without changing a word in the specification
as it stands to-day, I should have been awarded the
priority of invention by the courts. I am borne
out in this assertion by the highest legal authority.
In law, a caveat (Latin word, meaning “Let
him beware”) is a warning to other inventors,
to protect an incomplete invention; whereas in fact
the invention to be protected may be complete.
An application for a patent is presumed by the
law to be for a completed invention; but it may be,
and very often is, incomplete. It would often
make a very great difference if decisions were rendered
according to the facts in the case rather than according
to rules of law and practice, that sometimes work
great injustice to individuals.
As has been said in another chapter,
in the summer of 1874 I went to Europe in the interest
of the telephone, taking my apparatus, as then developed,
with me. I came home early in the fall and resumed
my experimental work. Many interesting as well
as amusing things occurred during these experiments.
I remember that in the fall or early
winter of 1874 I was in Milwaukee with my apparatus
carrying on some experiments on a wire between Milwaukee
and Chicago. I had my musical transmitter along,
and one evening, for the entertainment of some friends
at the Newhall House, a wire was stretched across
the street from the telegraph office into one of the
rooms of the hotel. A great number of tunes were
played at the telegraph-office by Mr. Goodridge, who
was my assistant at that time, which were transmitted
across the street, as before stated. In those
days it was a common practice in telegraphy to use
one battery for a great number of lines. For
instance, starting with one ground-wire which connected
with, say, the negative pole of the battery, from the
positive pole two, three or a half-dozen lines might
be connected, running in various directions, connecting
with the ground at the further end, thus completing
their circuits. For use in transmitting tones
across the street that evening we connected our line-wire
on to the telegraph company’s battery, which
consisted of 100 or more cells, and which had four
or five more lines radiating from the end of the battery
to different parts of Wisconsin. Our line was
tapped on to the battery (without changing any of
its connections) twenty cells from the ground-wire.
In transmitting, each vibration would momentarily shut
off these twenty cells from the lines that were connected
with the whole battery. The effect of this (an
effect that we did not anticipate at the time) was
to send a vibratory current out on all the lines that
were connected with that single battery as well as
across the street. A great many familiar tunes
were played during the course of an hour or two which,
unconsciously for us, were creating great consternation
throughout the State of Wisconsin, in many of the offices
through which these various lines passed.
Next morning reports and inquiries
began to come in from various towns and cities west,
northwest and north, giving details of the phenomena
that were noticed on the instruments located in the
various offices along the lines. They reported
their relays as singing tunes; one party said he thought
the instruments were holding a prayer-meeting from
the fact that they seemed to be singing hymn-tunes
for quite a while, but this notion was finally dissipated,
because they grew hilarious and sang “Yankee
Doodle.”
One operator, up in the pine woods
of northern Wisconsin, did not seem to take the cheerful
view of it that some of the others did. He was
sitting alone in the telegraph-office that evening
when he thought he heard the notes of a bugle in the
distance; he got up and went to the door to listen,
but could hear nothing; but on coming back into the
room he heard the same bugle notes very faintly.
He was inclined to be somewhat superstitious and grew
very nervous; finally, on looking around, he located
the sound in his relay, but this did not help matters
with him. With superstitious awe he listened to
the instrument for a few moments, while it gave out
the solemn tones of “Old Hundred,” then
it suddenly jumped into a hilarious rendering of “Yankee
Doodle.” This was too much for our nervous
friend, and hastily putting on his overcoat, he left
the office for the night.
On another occasion, when I was giving
a lecture in one of the cities outside of Chicago,
where exhibitions of music transmitted from Chicago
were given, one of the operators along the line was
very much astonished by his switchboard suddenly becoming
musical. Orders had been given for the instruments
in all the local offices to be cut out of the particular
line that I was using. Hence the instrument in
this particular office was not in the circuit through
which the tunes were being transmitted. The wire,
however, ran through his switchboard, and owing probably
to a loose connection, or an induced effect, there
was a spark that leaped across a short space at each
electrical pulsation that passed through the line,
thus reproducing the notes of the various tunes played.
You will remember in one of the chapters
on sound (Volume II.), it is stated that a musical
tone is made up of a succession of sounds repeated
at equal intervals, and that the pitch of the tone
is determined by the number of sound-impulses per
second. Applying this law to the sparks, you
will be able to see how the switchboard played tunes
for the operator.
In the foregoing experiments in transmitting
musical tones telegraphically, I used a great many
different varieties of receivers. Some of them
were designed with metal diaphragms mounted over single
electromagnets, not unlike the receiver of an ordinary
telephone. These instruments would both transmit
and receive articulate speech when placed in circuit
with the right amount of battery to furnish the necessary
magnetism. However, they were not used in that
way at the time they were first made in
1874. These I called common receivers, as they
were designed to reproduce all tones equally well.
I designed and constructed another form of receiver,
based somewhat upon the theory of the harmonic telegraph.
This consisted of an electromagnet
of considerable size, mounted upon a wooden rod about
ten feet long. Mounted upon this rod were also
resonating boxes or tubes made of wood of the right
size to have their air-cavities correspond with the
various pitches of the transmitting-reeds, so that
each tone would be re-enforced by some one of these
air-cavities, thus giving a louder and more resonant
effect to the musical notes.
Here were two types of receiver, one
that would receive one sound as well as another, but
none of them so loud, while the other was constructed
on the principle of selection and re-enforcement, so
that a particular note would be sounded by the box
having a cavity corresponding to the pitch of the
tone, and was much louder and of much better quality
than I could get from the diaphragm receiver.
One of these receivers pointed to the harmonic telegraph
and the other to the speaking telephone. I knew
that I had a receiver that would reproduce articulate
speech or anything else that could be transmitted.
My first conceptions of an articulate
speech-transmitter were somewhat complicated.
I conceived of a funnel made of thin metal having a
great number of little riders, insulated from the
funnel at one end and resting lightly in contact with
the funnel at the other end. These riders were
to be made of all sizes and weights so as to be responsive
to all rates of vibration. In the light of the
present day we know that such an arrangement would
have transmitted articulate speech, but perhaps not
so well as a single point would do when properly adjusted.
My mind clung to this idea till in the fall of 1875,
when an observation I made upon the street changed
the whole course of my thinking and solved the problem.
The incident I refer to took place in Milwaukee, where
I was then experimenting. One day while out on
an errand I noticed two boys with fruit-cans in their
hands having a thread attached to the center of the
bottom of each can and stretched across the street,
perhaps 100 feet apart. They were talking to each
other, the one holding his mouth to his can and the
other his ear. At that time I had not heard of
this “lovers’ telegraph,” although
it was old. It is said to have been used in China
2000 years ago.
The two boys seemed to be conversing
in a low tone with each other and my interest was
immediately aroused. I took the can out of one
of the boy’s hands (rather rudely as I remember
it now), and putting my ear to the mouth of it I could
hear the voice of the boy across the street. I
conversed with him a moment, then noticed how the cord
was connected at the bottom of the two cans, when,
suddenly, the problem of electrical speech-transmission
was solved in my mind. I did not have an opportunity
immediately to construct an instrument, as I had a
partner who was furnishing money for the development
of the harmonic telegraph and would not listen to
any collateral experiments. I remember sitting
down by this partner one day and telling him what
I could do in the way of transmitting speech through
a wire. I told him I thought it would be very
valuable if worked out. He gave me a look that
I shall never forget, but he did not say a word.
The look conveyed more meaning than all the words
he could have said, and I did not dare broach the subject
again.
However, as soon as I found opportunity,
without saying a word to anybody except my patent
lawyer, I filed a description, accompanied by drawings,
of a speaking telephone which stands in history to-day
as the first complete description on record of the
operation of the speaking telephone. It described
an apparatus which, when constructed, worked as described,
and it is a matter of history that the first articulate
speech electrically transmitted in this country was
by a transmitter constructed on the principle described,
and almost identically after the drawings in my caveat.
While the transmitter described in this caveat was
not the best form, it would transmit speech, and it
contained the foundation principle of all the telephone
transmitters in use to-day.
There are two methods of transmitting
speech. One is known as the magneto method and
the other that of varying the resistance of the circuit.
My first transmitter was devised on the latter principle.
I append to this extracts from my
specification filed Fe, 1876:
To All Whom It May Concern: Be
it known that I, Elisha Gray of Chicago, in the
County of Cook and State of Illinois, have invented
a new art of transmitting vocal sounds telegraphically,
of which the following is a specification: It
is the object of my invention to transmit the
tones of the human voice through a telegraphic
circuit, and reproduce them at the receiving-end
of the line, so that actual conversations can
be carried on by persons at long distances apart.
I have invented and patented methods of transmitting
musical impressions or sounds telegraphically,
and my present invention is based upon a modification
of the principle of said invention, which is
set forth and described in letters patent of
the United States, granted to me July 27, 1875, respectively
numbered 166,095 and 166,096, and also in an application
for letters patent of the United States, filed
by me, Fe, 1875. My present belief
is that the most effective method of providing
an apparatus capable of responding to the various
tones of the human voice is a tympanum, drum,
or diaphragm, stretched across one end of the
chamber, carrying an apparatus for producing
fluctuations in the potential of the electric circuit
and consequently varying in its power. The vibrations
thus imparted are transmitted through an electric
circuit to the receiving-station, in which circuit
is included an electromagnet of ordinary construction,
acting upon a diaphragm to which is attached
a piece of soft iron, and which diaphragm is
stretched across a receiving vocalizing chamber C,
somewhat similar to the corresponding vocalizing chamber
A.
The diaphragm at the
receiving-end of the line is thus thrown
into vibrations corresponding
with those at the
transmitting-end, and
audible sounds or words are produced.
The obvious practical application of
my improvement will be to enable persons at a
distance to converse with each other through
a telegraphic circuit, just as they now do in each
other’s presence, or through a speaking-tube.
I claim as my invention
the art of transmitting vocal sounds or
conversations telegraphically
through an electric circuit.
This specification was accompanied
by cuts of the transmitter and receiver connected
by a line-wire and showing one person talking to the
transmitter and another listening at the receiver.
These cuts may be seen in various books on the subject
of telephony.