IMPROVEMENTS IN TRANSMITTERS FOR TELEPHONES OR VOCAL SOUND TELEGRAPHS
Year: 1880

page_text: LETTERS PATENT to Robert Minturn Lockwood and Samuel Hubbard
Bartlett, of the City, County, and State of New York, in the United States
of North America, for an Invention of "IMPROVEMENTS IN TRANSMITTERS
FOR TELEPHONES OR VOCAL SOUND TELEGRAPHS."
COMPLETE SPECIFICATION filed by the said Robert Minturn Lockwood and
Samuel Hubbard Bartlett at the Office of the Commissioners of Patents on the
15th June 1880.
ROBERT MINTURN LOCKWOOD and SANUEL HUBBARD BARTLETT, of the City,
County, and State of New York, in the United States of North America.
"IMPROVEMENTS IN TRANSMITTERS FOR TELEPHONES OR VOCAL SOUND TELE-
GRAPHS."
Our Invention differs essentially from telephonic transmitters hitherto devised
in that its effectiveness depends not upon the mechanical vibration or bodily
movement of a diaphragm or its equivalent device to which the atmospheric sound
waves are directed, but upon what we term molecular movement, inasmuch as
Baid waves are transmitted from molecule to molecule of a non resonant material,
which as a body remains stationary while serving as a conducting agent between
the atmospheric sound waves and the microphone which controls the volume,
pitch, and variations of sound transmitted to and through the wires. In the
practice of our Invention a microphone of any suitable character and provided
with suitable transmitting wires is supported and either wholly or partially
imbedded in cork, light wood, or other non resonant material, so that when sound
waves produced by the voice or other agency are directed against the outer
surface of the non resonant material a molecular disturbance is produced in said
material, which is communicated to the microphone and causes a similar dis-
turbance therein and the original sound, modified thereby as a manisfestation of force,
is transmitted through the microphone to the wires and is reproduced at other
portions of the circuit in any suitable receiver.
In the accompanying Drawings Figure 1 represents our improved transmitter in
section.
the anthan plates only partially imbedded and

page_text: construction shown in Figure 2 with the carbon button removed, and Figure 4 is
a sectional view similar to Figure 2 showing a modification in the form of the
carbon button.
In the above Figures of Drawings like letters of reference are employed to
indicate like parts wherever such may occur, and in these Figures the microphone
is represented as composed of two bars A, A, arranged in or about in the same
plane with their inner ends approaching each other but out of actual contact, as
shown. These bars are preferably of carbon of the kind well known to electricians,
but they may be of any suitable conducting material, such as motal, which however
as far as our experiments have extended has been found inferior to the carbon in
its results. The adjacent ends of the bars A, A, have semicylindrical notches cut
in them opposite each other forming a circular opening between the bars for the
reception of a pin b on the lower face of a small button or disc B of carbon or
other conducting material, similar to that of which the bars A, A, are composed,
maid button resting by gravity on the inner ends of the bars. In Figuro 4 the
button is represented as made in the form of a small sphere, and rests in a
semispherical socket formed in the upper faces of the bars at their adjacent ends.
The microphone thus formed is imbedded in a mass or block C of cork, light
wood, or other material, possessing as far as may be the peculiar non resonant
property of cork. This block or body of the transmitter may be mado in any suitable
form, such as that of a cube, that shown being in the form of a short cylinder
supported upon a base plate D, to which the binding posts d, d, may be attached, as
shown, the wires A', A, attached to the bars A, A, and passing out through the
block being connected therewith, and thence with the main line wires or directly
with the latter as preferred, the former arrangement facilitating the detachment of
the transmitter when desired. The block of non resonant material may have a
chamber formed in it, as shown at B¹, the inner adjacent ends of the bars A, A,
projecting into said chamber, leaving them only partially imbedded while still
supported in the non-resonant material, but it is preferred to imbed them in said
material throughout their whole length, and to fill the aperture over the button for
affording access thereto with a plug of non resonant material out of actual contact
with the button, but sufficiently near thereto to prevent its displacement in
handling the transmitter. We prefer also to snugly enclose the block of non
resonant material in a metal cylinder or casing E having a screw cap or cover E¹,
and to wrap said case with a sleeve of leather, rubber, canton flannel, or other
soft non resonant material, as tending still further to prevent mechanical vibrations
but these may be omitted, as without them the non resonant block C is found to
answer admirably for the body of the transmitter with the microphone embedded
therein as explained.
In the operation of the apparatus the sound waves produced in the air by the
voice or other sound producing agent strike the external surface of the cork (or of
its covering described), but owing to the inert nature of the cork they cause no
mechanical vibration or bodily movement of the latter, and must therefore transmit
their force through the mass of non resonant material to the bars A, A, and thence
to the button B, or its equivalent, by molecular action, but inasmuch as the degree
or force of the molecular disturbance varics with that of the impact on the surface
of the cork or its covering, it follows that the molecular action in passing from
the bars to the button will be more or less modified, as the surfaces in contact
between the button and the bars provide different conditions from those existing in
the homogeneous material of the bars themselves. This modification or disturbance
in the relation of the button to the bars, although not susceptible to mechanical
measurement, and consisting in a changed condition of the points of contact between
the button and the bars rather than in any change in their relative positions, is
responsive to every modification of the sound waves brought to bear against the
surface of the cork, and the microphone being thus responsive to every variation in
the original sound insures its transmission through the wires to any suitable receiver.
The office of the pin b in the button is simply to keep the latter in position, tho

page_text: flat lower face of the button resting upon the flat surfaces of the bars being found
to give better results than any other relation of the parts thus far devised, though
the ball resting in the semi-spherical socket, as described, has been found to answer
the purpose very well, but its tendency to become wedged in the socket makes it
inferior to the flat button. It will be apparent that the form and construction of
the apparatus may be varied, and we do not therefore restrict ourselves to the
form and arrangement shown so long as we imbed the microphone wholly or
partially in a non resonant material, and obtain the desired action through what
we have designated as molecular disturbance in contradistinction from the so
called mechanical vibration of a diaphragm or equivalent device heretofore
employed in telephone transmitters.
The power of the suppressed or imbedded microphone may be increased by the
addition of a magnet and suitable helices, the wires of which are connected with
said microphone, but as this feature is to be made the subject matter of another
Patent it is unecessary to describe it here in detail.
Having now described our Invention and the manner in which the same is to
be carried into practical effect, what we claim and desire to secure by Letters
Patent is,
1st. The method and means for transmitting sound waves, as hereinbefore
described and set forth.
2d. In a transmitter for telephones or vocal sound telegraphs, a block of non
resonant material having plates or bars of carbon or other conducting material
either wholly or partially imbedded within it.
3d. The block of non resonant material having conductors imbedded within it,
and wires extending therefrom for connecting them with the main line current.
4th, The block of non resonant material having the conducting bars or plates
imbedded within it in combination with the interposed button, as set forth.
5th. The non resonant block in which the conducting bars or plates are imbedded
combined with a metallic enclosing case.
6th. The combination with the non resonant block having the conducting bars
or plates imbedded in it of the metallic enclosing case and the flexible non resonant
cover thereto, as specified.
In witness whereof, we, the said Robert Minturn Lockwood and Samuel
Hubbard Bartlett, have hereunto set our hands and seals, this Fifteenth day
of June, in the year of our Lord One thousand eight hundred and eighty.
ROBERT MINTIRN LOCKWOOD