IMPROVEMENTS IN TELEPHONE TRANSMITTERS
Year: 1885

page_text: J, ALEXANDER MELVILLE CLARK, of the firm of A. M. and Wm. Clark, of
53, Chancery Lane, in the County of Middlesex, Fellow of the Institute of Patent
Agents, do hereby declare the nature of the said Invention for "IMPROVEMENTS
IN TELEPHONE TRANSMITTERS" (a communication to me from abroad by The
Long Distance Telephone Company (Incorporated) of 53 Broadway, New York
City, United States of America) and in what manner the same is to be performed,
to be particularly described and ascertained in and by the following statement:-
This invention relates to the class of telephones known as transmitting telephones
and is designed to be used in a battery circuit in connection with a magneto-
receiving telephone, either with or without an intermediate induction coil.
The object of this invention is to provide a light portable telephone transmitter
which may be readily held in the hand while carrying on telephonic communi-
cation.
The Invention is illustrated in the accompanying drawing in which
Figure 1 is a front elevation of the improved telephone transmitter.
Figure 2 is a longitudinal section of the same. Figure 3 is a transverse section
taken on line xx in figure 2 and Figure 4 is a diagram showing the manner of
connecting the transmitter in the telephone circuit.
Similar letters of reference indicate the same parts in all the figures of the
drawing.
The invention consists essentially in a granulated semi-conductor, such as
granulated or coarsely powdered carbon, maintained normally under compression ;
also in apparatus for utilizing such a semi-conductor in a transmitting telephone.
Referring to the drawings the telephone has a diaphragm cell I provided with a
mouth piece J, of the usual form, which clamps the diaphragm K, in the cell. In
the centre of the diaphragm cell is formed a cylindrical cavity L, in which is
placed an elastic rubber tube M, having at opposite ends the conducting plates N N¹,
which together with the said elastic tube M, forms a chamber O which is filled
with granulated carbon. In the body of the diaphragm cell I, at diametrically
opposite points are placed metallic nuts P, P', which are in electrical communi-
cation with the plates N, N¹, and which receive the pivotal screws. Q, Q',
passing through spring arms R, R', attached to the handle S, and form the pivotal
support of the transmitter as well as the electrodes by which the current is
introduced into the instrument. The diaphragm K, carries a stud n which presses
upon the centre of the conducting plate N, and in a cavity formed in the back of
the diaphragm cell I, is secured a cross bar o provided with a central adjusting
screw p, which bears upon the centre of the conducting plate N', and is employed

page_text: to maintain or vary the normal pressure upon the granulated carbon contained in
the elastic tube M.
The handle S, of the telephone transmitter is made tubular to receive the double
conductor T, containing the wires m, m³, communicating with the curved arms R, R¹.
The current arrives at the granulated carbon contained in the elastic cell M, from
one pole of the battery U, (Figure 4) through the wire m¹, curved arm R³, screw Q¹,
and nut P¹, wire q, and plate N¹, and passes from thence through the plate N, wire r,
nut P, screw Q, arm R, and wire conductor m, to the primary wire of the induction
coil V, which is connected with the remaining pole of the battery; one end of the
secondary wire of the coil goes to the ground, the other end being connected with
the line: Sounds made in the vicinity of the mouth piece J, vibrate the diaphragm K,
and the diaphragm acting through the stud n exerts a greater or less pressure upon
the granulated carbon contained in the elastic cell, thus altering its conductivity
and producing fluctuations in the current by which speech is transmitted along
the line.
The improved transmitter may be used in any desired position, and adapts itself
readily to varying inclinations of the head of the user. It is particularly adapted
to the transmission of messages which are read from manuscripts or books and
to dictating to a stenographer or amanuensis who may be located in another
apartment.
The form of transmitter which I have described, is adapted to the multiplex
system of telephony in which a number of variable resistances are operated by a
single transmitter diaphragm, the contents of each elastic cell being connected with
its own battery and induction coil, the secondary wires of the induction coils being
all connected with a single line wire and with a single ground.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
I claim is
1. In a telephone transmitter, a granulated disintegrated semi-conductor main-
tained normally under pressure, the pressure being variable by the vibration of the
transmitter diaphragm as herein specified.
2. The combination in a telephone transmitter, of an elastic non-conducting cell,
a granular filling of conductive material, contained in the said cell, and conducting
plates applied to the ends of this elastic cell in contact with the granulated
conductor, one of the said plates being supported rigidly, the other being movable
and pressed by the transmitter diaphragm, as herein specified.
3. The combination in a transmitting telephone, of the rigid cell supporting the
diaphragın, the elastic cell containing a granular conductor and an adjusting device
for regulating the compression of the granular conductor, as specified.
4. The combination in a telephone transmitter of the rigid diaphragm cell I, the
elastic cell M, and granular filling contained therein, conducting plates N, N¹,
conducting pivotal screws Q, Q¹, conducting arms R, R¹, and conducting wires as
herein specified..
5. The combination in a transmitting telephone, of the diaphragm K, the elastic
cell M, a granular conductor contained within the elastic cell, and between the
conducting plates N, N¹, and the adjusting screw p, as herein specified.