IMPROVEMENTS IN AND CONNECTED WITH TELEPHONES
Year: 1885

page_text: I PHILIP MIDDLETON JUSTICE of 55 and 56 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 AND CONNECTED WITH TELEPHONES
A communication to me from abroad by Francis Blake of Weston, Massachusetts
United States of America Electrician and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:
A mass
The invention relates to that class of telephone transmitters in which a powdered
or granulated conducting material forms that portion of the telephone circuit the
resistance of which is varied under the action of sound waves. I employ a
horizontal diaphragm which receives the sound waves upon its under surface, and
has a mass of powdered or granulated conducting material laying loosely upon its
upper surface and forming the variable resistance portion of the circuit.
of such material in a loose condition has a very high resistance as compared with
the same mass in a solid or compact form; and the vibrations of the diaphragm
under the action of sound waves tend constantly to throw the loose conducting
material upward and prevent it from becoming so compacted or compressed as to
change the specific resistance of the mass.
One part of the invention relates to the construction of an electrode which is
buried in the granulated material and admits such free movement thereof, and at
the same time gives a large cross section and consequently a comparatively low
resistance to that part of the circuit. I am thus enabled to accomplish results
with a single cell battery which might otherwise require a larger number of cells.
Another part of my invention relates to a method of connecting the diaphragm
with the electrode which is buried in the loose material, so that the diaphragm is
strained and so that the vibrations of the diaphragm shall affect the loose material
more uniformly and shall be communicated directly to said buried. electrode.
unstrained diaphragm, by reason probably of differences of tension between
different portions, is liable to vibrate differently under the action of sound waves
at different points equally distant from the centre, and thus may fail to cause
changes in the resistance of the loose material corresponding faithfully to the form
of the sound waves.
An

page_text: The vibrations of the electrode, due to its mechanical connection with the
diaphragm assist in maintaining the loose condition of the granulated material.
IN THE DRAWINGS.
Fig. 1. is a sectional elevation of my new transmitter embodying the above
mentioned improvements.
Fig. 2. is a plan of the same with the clamping plate and the granulated
conductor omitted.
Fig. 3. is a plan of the diaphragm.
Fig. 4. is a plan of the sieve electrode.
Fig. 5. is a plan of a non-conducting washer used to separate the diaphragm from
the sieve electrode.
Fig. 6. is a plan of a non-conducting post or block inserted between the
diaphragm and the sieve electrode.
Fig. 7. is a partial sectional elevation showing a modification.
All the parts are shown of approximately full size, and I may add that by
experiment I have found that the size and proportions, about as shown are those
best adapted for the use of the 'instrument with ordinary receivers.
A. is the bed or support for the telephone and contains the aperture through
which speech is uttered; B is a ring of non-conducting material resting on the
bed A, and b, is a metallic ring resting on the bed A. within the ring B. and
forming the seat of the diaphragm. In one form of construction, the rings B and b,
are both of non-conducting material and are formed in one piece, the bed A. in
such case being omitted D, is a metallic diaphragm resting at its edges upon the
ring or seat b.
The diaphragm as above stated, is one of the electrodes, and in practice it is
connected with one of the circuit wires through the seat b, when that seat is
metallic, or directly with such wires when the seat bis integral with the ring B,
and is of non-conducting material. S is a wire sieve electrically separated from
the diaphragm by a washer w, of non-conducting material. P is a metallic
clamping plate having a boss or ring projection p, that rests upon the sieve at the
edge of the latter. The plate P and the ring B have the same diameter; and so
likewise the boss of the plate P, the sieve S, the washer w, the diaphragm D, and
the seat b, are equal in diameter; and accordingly the different parts of the
instrument are held together by screws, (I use but four) passing through the
plate P, and the ring B, and into the bed A. when a bed is employed.
Electrical connection is made between the sieve-electrode S. and its circuit wire
through the metallic clamping plate P. C, is a finely divided or granulated con-
ducting material (I use powdered carbon) filling the instrument above the diaphragm
to within a short distance of the plate P. The grains are of a size that permits them
to pass freely through the sieve which is buried in their mass. The plate P, has a hole
through which the granulated conductor is poured. This hole is closed by a screw
plug E. L, is a post or block of non-conducting material inserted between the
diaphragm and the sieve, thereby straining the diaphragm. It also gives to both
the diaphragm and the sieve a conical form; and, being firmly clasped between
the diaphragm and the sieve, as between two springs, causes the latter mechanically
to partake of the vibrations of the former. When the instrument is connected up
for use, as before stated one wire leads to the diaphragm, and the other to the
sieve. The diaphragm and the sieve thus become electrodes, the granulated
conductor making the electrical connection between them. Further description of
the mode of operation of the instrument as a whole is unnecessary. The instrument
thus constructed will remain in adjustment no matter what may be the character
of the sounds falling upon the diaphragm.
Vocal sounds transmitted by it are remarkably faithful copies of the original;
'and above all the instrument is superior to all other telephones with which I
-am acquainted in preserving the loudness of the sounds transmitted, I will add

page_text: however, that while the form of construction described and shown gives the best
results as a whole, I have found that some of the details of construction are
advantageous to a greater or less extent independent of other details. Thus the
advantage derived from the action of a strained diaphragm acting upon loose
material forming the variable resistance portion of the circuit is not dependent
upon the use of the diaphragm as one electrode, nor upon the use of the sieve as
the other electrode, but will be secured when either the diaphragm or the sieve is
used for one electrode and a ring at the outer edge, of the loose material is employed
as the other electrode. That is, in the instrument shown, one of the circuit wires
may be made to connect either with the diaphragm D, or the sieve S and the other
with the boss p. of the clamping plate P. But when the sieve and the ring are
made to serve as the electrodes of the instrument represented in the drawings they
must be separated electrically by a washer; (for this construction see Fig. 7. where
the additional washer is marked w¹).
Neither is the advantage which is due to the mechanical connection between the
sieve and the diaphragm wholly dependent either upon the use of the diaphragm
as an electrode or upon the use of the diaphragm in a horizontal position. There
is great advantage gained as to loudness even when the diaphragm is out of the
circuit by rigidly connecting the centre of the diaphragm with the sieve buried in
the loose conducting material so that the sieve will partake of the vibrations of the
diaphragm, and this even if the instrument is turned up so as to be used
substantially at a right angle to the position shown. The present instrument may
be so used by making the sieve serve as one electrode and the boss, of the ring Pas
the other, inserting a non-conducting washer between them, and causing the sieve
to partake of the vibrations of the diaphragm in the manner now shown.
Having now particularly described and ascertained the nature of the said
invention as communicated to me from abroad by my foreign correspondent, and
in what manner the same is to be performed I declare that what I claim is
1st In a telephone employing a granulated conducting material as the variable
resistance portion of the circuit, two horizontal electrodes, one serving as the
transmitting diaphragm and carrying such material loosely upon its upper surface,
and the other being a sieve buried in such material and allowing such material to
pass freely through it, substantially as described.
2nd In a telephone employing a granulated conducting material as the variable
resistance portion of the circuit two horizontal electrodes mechanically connected to
vibrate together, one serving as the transmitting diaphragm and carrying such
material loosely upon its upper surface, and the other being a sieve buried in such
material, and allowing such material to pass freely through it, substantially as
described.
3rd In a contact telephone employing granulated conducting material as the
variable resistance portion of the circuit, a transmitting diaphragm in mechanical
contact with said granulated material, and an electrode buried in said granulated
material and allowing said material to pass freely through it, the said electrode
being mechanically connected to the said diaphragm, at the centre of the latter, to
partake of its vibrations substantially as described.
4th In a telephone employing a granulated conducting material as the variable
resistance portion of the circuit a transmitting diaphragin carrying such material
loosely upon its upper surface, and strained to a conical form, substantially as
described.