Improvements in Telephone Transmitters.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
Improvements in Telephone Transmitters.
I, JOSEPH VINCENT COLLINGWOOD, of 20, Fairholme Road, Great Crosby, in the
County of Lancaster, Electrician, do hereby declare the nature of this invention
to be as follows:-
My invention relates to microphonic telephone transmitters, or those in which
the sound waves impart to and fro movements to the transmitting diaphragm, and
these to compressed bodies of carbon, thus varying the resistance by pressure.
The object of the invention is to provide a transmitter which will be capable of
transmitting sounds or words spoken into it clearly and to a great distance, and
at the same time be free from external sounds, also one in which there are no
loose granules of carbon which are so liable to consolidate or fall out, thus inipair-
ing the sensitiveness of the diaphragm, and one in which no adjustment or
damping arrangement is necessary.
In carrying the invention into effect, I form my instrument with a carbon
receptacle having sunk on the front face of it a number of conical or other shaped
cavities, each adapted to receive a ball of compressed carbon. In proximity to
the carbon receptacle and in a parallel plane therewith is a carbon diaphragm
securely fixed at its edges, and capable of being set into vibration by the sound
waves striking against it. It is protected from injury or breakage by a wire
cage with bell mouth front. This diaphragm is the first to receive the sound
waves entering the transmitter, and being very thin is capable of being instantly
set into vibration by the slightest sound wave. The diaphragm is separated from the
carbon receptacle by an air space, and the carbon balls are placed loosely and
separately in the cavities between the two carbon surfaces so that the current
The conical
flows through the balls and acts on all the loose contacts at once.
shape of the cavities is utilised to keep the balls in contact with the diaphragm.
The current passes by way of the diaphragm, balls and carbon receptacle. The
sound waves impart to and fro movements to the carbon diaphragm, thus sub-
jecting the balls to varying pressures and the current passing through them to a
varying electrical resistance.
In thus describing my invention, I wish it to be understood that I do not
confine myself to the cavities being made of conical shape or to the bodies of car-
bon being made in the shape of balls, as other shapes both of the cavities and of
the carbon bodies may be adopted, so long as the object is attained of keeping
the bodies of carbon in the receptacle in loose contact therewith and with the
diaphragm.
Furthermore, the positions of the carbon diaphragm and receptacle may be
reversed, that is, the receptacle may be placed in front with the cavities for the
balls on its rear face, and the diaphragm (which in such case may be made of
thicker material) immediately behind, with an air space between. In such case,
however, I place in front immediately behind the bell mouth, a diaphragm of
pine or other suitable material, which is mounted in the brass frame which holds

page_text: the carbon receptacle, with a rubber washer placed between the metal and wood.
Instead of carbon other conducting material might be employed.
Dated this 1st day of March 1898.
WM. P. THOMPSON & Co.,
of 6, Lord Street, Liverpool, Patent Agents for the Applicant.
Improvements in Telephone Transmitters.
I, JOSEPH VINCENT COLLINGWOOD, of 20, Fairholme Road, Great Crosby, in the
County of Lancaster, Electrician, do hereby declare the nature of this invention
and in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement:-
My invention relates to microphonic telephone transmitters, or those in which
the sound waves impart to and fro movements to the transmitting diapliragm,
and these to compressed bodies of carbon, thus varying the resistance by pressure.
The object of the invention is to provide a transmitter which will be capable of
transmitting sounds or words spoken into it clearly and to a great distance, and
at the same time be free from external sounds, also one in which there are no
loose granules of carbon which are so liable to consolidate or fall out, thus impair-
ing the sensitiveness of the diaphragm, and one in which no adjustment or
damping arrangement is necessary.
The invention will be understood from the following description, reference
being had to the accompanying drawings, in which,
Figure 1 is a sectional view of my microphonic telephone transmitter;
Figure 2, a front view of the carbon receptacle showing the cavities therein.
Referring to these figures, I form my instrument with a carbon receptacle or
diaphragm A having sunk on the front face of it a number of conical or other
shaped cavities B, each adapted to receive a ball C of compressed carbon.
In proximity to the carbon receptacle and in a parallel plane therewith is a
carbon diaphragm D securely fixed at its edges, and capable of being set into
vibration by the sound waves striking against it. It is protected from injury or
breakage by a wire cage E with bell mouth front F. This diaphragm D is the
first to receive the sound waves entering the transmitter, and being very thin is
capable of being instantly set into vibration by the slightest sound wave. The
diaphragm D is separated from the carbon receptacle A by an air space, and the
carbon balls C are placed loosely and separately in the cavities between the two
carbon surfaces A and D so that the current flows through the balls and acts on
all the loose contacts at once. The conical shape of the cavities is utilised to
keep the balls in continuous contact with the diaphragm. The current passes
by way of the diaphragm, balls and carbon receptacle. The sound waves impart
to and fro movements to the carbon diaphragm, thus subjecting the balls to
varying pressures and the current passing through them to a varying electrical
resistance.
In thus describing my invention, I wish it to be understood that I do not con-
fine myself to the cavities being made of conical shape or to the bodies of carbon
being made in the shape of balls, as other shapes both of the cavities and of the
carbon bodies may be adopted, so long as the object is attained of keeping the
bodies of carbon in the receptacle in loose contact therewith and with the
diaphragm.
Furthermore, the positions of the carbon diaphragm and receptacle, may be

page_text: reversed, that is, the receptacle may be placed in front with the cavities for the
balls on its rear face, and the diaphragiu (which in such case may be made of
thicker material) immediately behind, with an air space between. In such case,
however, I place in front immediately behind the bell mouth, a diaphragm of
pine or other suitable material, which is mounted in the brass frame which
holds the carbon receptacle, with a rubber washer placed between the metal and
wood. Instead of carbon other conducting material might be employed.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:-
1. The improvement in telephone transmitters, which consists in forming them
with a diaphragm or receptacle of carbon or other suitable material having sunk
on its face a number of cavities each adapted to receive loosely and separately
therein a ball or other shaped body of compressed carbon, in combination with
a diaphragm located opposite and adjacent to the cavitied face aforesaid against
which the balls are adapted to be kept in contact, one of these diaphragms being
adapted to receive the sound waves and transmit them to the carbon balls, where-
by the latter are subjected to varying pressures and the current passing through
them to a varving electrical resistance substantially as described.
2. In a telephone transmitter having a diaphragm with its surface formed with
a number of cavities or depressions in which are located balls or other shaped
bodies of compressed carbon, placed loosely and separately therein, and another
diaphragm located in proximity to the surface of said diaphragm while leaving
an air space between, forming said cavities in the one diaphragm in such a way
that the compressed bodies aforesaid will normally roll or come into, and be
kept in contact, with the surface of the adjacent diaphragm, substantially as and
for the purpose described.
3. The improved microphonic telephone transmitter herein described and illus-
trated in the accompanying drawing.