Improvements in TelEPHONE TRANSMITTERS
Year: 1882

page_text: LETTERS PATENT to Edward Griffith Brewer, of 33, Chancery Lane, in the
County of Middlesex, for an Invention of "Improvements in TelEPHONE
TRANSMITTERS." A communication from abroad by Joseph Olmsted, of New
York, United States of America.
PROVISIONAL SPECIFICATION left by the said Edward Griffith Brewer at
the Office of the Commissioners of Patents on the 21st January 1882.
_EDWARD GRIFFITH BREWER, of 33, Chancery Lane in the County of Middlesox.
"IMPROVEMENTS IN TELEPHONE TRANSMITTERS.' (A communication from abroad
by Joseph Olmsted of New York, United States of America.)
"
This invention refers to a novel construction of the electrodes or circuit con-
trolling portion of the instrument, whereby the operation of the instrument in
transmitting sounds is greatly improved, the constancy of the adjustment
increased and whereby also the occurrence of the hissing spluttering and other
foreign sounds in the receiver caused by abnormal action of the transmitter is
largely avoided, and the instrument is made capable of transmitting with perfect
accuracy and without any rattling or confusion of tone, all sounds, whether loud or
soft and whether produced near to or remote from the instrument.
The invention also refers to other novel features of construction relating more
particularly to the adjusting devices and the means employed for holding the
electrodes in position.
In telephone transmitters as heretofore usually constructed, but one electrode
has been employed for making contact with the electrode or contact which is
attached to, or connected with the diaphragm so as to be put in motion thereby,
and in those instances where two electrodes have been used, resting upon the
diaphragm in multiple arc, springs have been employed for compelling contact and
independent adjusting devices have been used for the two electrodes.
This improved transmitter differs from prior instruments of its class in that a
multiplicity of electrodes are employed resting against the same and opposite
electrode connected with the diaphragm each electrode being freely pivoted so as

page_text: to rest by its own weight upon the diaphragm electrode, while further said
electrodes have a common support adjustable by suitable devices so that they are
adjusted together. The electrodes being symmetrically arranged and each resting
by its own weight upon the common electrode carried by the diaphragm the
natural and normal contact is the same for all whereas in the case of spring
supported electrodes, there are no means of determining the force which tends to
hold the electrodes in contact with the diaphragm, and it is hence impossible to
have the same initial or normal contact for all. By this arrangement the initial or
normal contact is approximately the same for all. Moreover (as there is a multi-
plicity of electrodes, and they are arranged so that the current passes through
them and the opposite electrode in multiple arc, a defect in one will not seriously
affect the operation of the instrument, and as the electrodes are hung upon a
common adjustable support the initial force tending to hold them in contact can
be readily adjusted for all by one and the same adjustment.
The form of the pivoted or swinging electrode employed is also peculiar, and is
such that an adjustinent to increase the initial force tending to hold it in contact
with the opposite or the diaphragm electrode will also vary the angle of impinge-
ment of the electrode carried by the diaphragm with the pivoted olectrodes, and
decrease the tendency of the latter to yield or move under the action of the
diaphragm electrode; great delicacy of contact and of action is also secured by
employing an electrode consisting of a thin sheet of carbonized paper or cardboard,
resting with its edge against the opposite electrode. A compound electrode
consisting of a number of such plates freely pivoted and connected in multiple arc
with an opposite electrode or electrodes, is exceedingly constant in its action, and
transmits with great accuracy and without any rattling or confusion of tono all
sounds whether loud or soft, and whether produced at a distance-from-the
instrument or in immediate proximity thereto.
As one of the methods of carrying out this invention, upon a common support
is pivotted a series of thin plates of carbonized cardboard or paper placed side by
side, and resting with their edges upon a metallic bar having a platinized contact
surface, which bar is attached to a diaphragm and is made to move to and fro
bodily with the diaphragm.
The carbon plates are free to move up and down in a vertical plane and the
supporting rod for said plates is nearly in the same horizontal plane with the
electrode with which said plates make contact and are partially supported. The
supporting rod may however be above or below tho horizontal line passing through
the diaphragm electrode. The lower edge of the plates is bevilled or the plates
are inclined so that the line of the lower or supported edge of each plate is inclined
to the diaphragm electrode. As the diaphragm electrode vibrates it is forced
against the plates, and tends to raise them, If the inclination of the edge of the
plates to the line of notion of the diaphragm electrode be made more abrupt, the
resistance opposed by the plates to the motion of the diaphragm electrode will le
more decided, and it is proposed to take advantage of this fact for varying the
adjustment of the instrument, by making the support for the plate electrodes
adjustable to and from the diaphragm electrode, so as to vary the angle of
impingement of the diaphragm electrode against the edges of the plates. This
adjustment will also vary the initial contact, since the nearer the support upon
which the plates are pivotted is adjusted to the electrode with which they make
contact and are partially supported, the greater will be the portion of the weight
of each electrode supported by the opposite and partially supporting electrode.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Edward Griffith Brewer in the Great Seal Patent Office on the
21st July 1882.
"
EDWARD GRIFFITH BREWER of 33 Chancery Lane in the County of. Middlesex.
IMPROVEMENTS IN TELEPHONE TRANSMITTERS (A communication from abroad
"
by Joseph Olmsted of New York United States of America.)
This invention relates to telephone transmitters in which the current from a
galvanic battery passing through contact electrodes or points is varied by the
impingement of the air waves or vibrations accompanying vocal sounds upon some
portion of the instrument to which the electrodes are connected.
The invention herein described as applied in connection with transmitters
employing a disc or diaphragın but the novel electrode jor contact piece herein
described is applicable to other constructions of telephones or may be used as a
variable contact in a microphone.
In telephone transmitters it has heretofore been common to employ but one
electrode for making contact with the electrode which receives motion from the
diaphragm and in those cases where a number of electrodes have been employed
making contact abreast or in multiple arc with a number of opposite olectrodes or
a single electrode common to them all, springs have been employed for holding the
electrodes in contact and independent adjusting devices have been employed for
the various electrodos.
This invention consists first in a novel construction of telephone in which is
employed a series of independently pivotted electrodes forming together a compound
electrode and resting against an opposite electrode by their own gravity and
mounted upon a common adjustable support whereby the same or practically the
same initial contact is secured for all, and all may be adjusted together for varying
the contact. In former arrangements employing seperate adjusting dovices it is
impossible to determine the adjustment that will give the same contact for all
whereas in this arrangement, each electrode being actuated only by an invariable
force like gravity and all having a common adjustable support the adjustment of
the instrument can be accomplished with the certainity that the contact of all the
electrodes has been varied to the same extent for all.
This invention consists secondly in a novel contact or electrode composed of a
thin sheet of carbonized paper or cardboard, or of a number of such sheets arranged
side by side to make a compound electrode said sheet or sheets being mounted so as
to rest with its edge against the opposite electrode.
A compound electrode thus constructed is very constant in its action and
transmits sounds with great volume and accuracy.
Instead of carbonized paper a thin sheet of metal like platinum or german silver
is sometimes used resting in the same manner with its edge against the opposite
electrode. In the accompanying drawings, Figure 1 is a partial vertical section of
a transmitter embodying the invention. Figure 2 is a rear view of the operative
parts of the instrument the back being removed.
A represents the casing of the transmitter, B its mouth piece, and C the
metallic disc or diaphragm which is clamped between a ring D and a block E in
any suitable manner and is provided at its edge with a rubber dampening ring
after a manner common in instruments of this class. F is an electrode which is
attached to and moved with the diaphragm. This electrode consists of a longi-
tudinal bar, having a bevelled edge and provided at or near its centre with a
laterally projecting stud into which passes a screw by which said electrode is
ecured to the diaphragm.

page_text: The edge of the bar F which forms the contact edge is by preference of platinum.
G G represent thin sheets of carbonized cardboard or paper strung upon a rod H of
some conducting material and contained between two blocks II also attached to
the rod. The plates G G rest with their edges in contact with the edge of the
bar electrode F. The rod H is mounted in brackets K K which are of hard
rubber or similar non conducting material and are suspended or attached to
rods L L mounted upon the clamping ring D or any suitable portion of the
instrument. The non conducting brackets may be adjusted horizontally upon the
rods LL, thus carrying with them the supported bar H and the electrodes G and
adjusting the degree of initial contact between the electrodes of the instrument.
Upon the end of the conducting rod H is a binding screw N which serves for the
attachment of one portion of the circuit wire coming from the galvanic battery.
Electrical connection is made with the electrode F by means of binding screw O
which is mounted directly upon the clamping ring D of metal, the latter being
electrically connected with the diaphragm by means of a screw P which passes
through the ring D and against or into the edge of the diaphragm.
M M are set screws which serve to hold the brackets K at any desired position
upon the rods L. R represents the induction coil of the transmitter the primary
coil of which makes a portion of a local circuit including the electrodes G. F and a
galvanic battery while its secondary coil is connected to line in the well known
manner. The various parts are electrically connected in the ordinary way well
understood in the art, and the instrument operates after the manner of any contact
telephone or microphone. The transmission of sounds is however accomplished
with great distinctness and volume of tone and the instrument will operate for an
indefinite period without adjustment..
The carbonized sheets G G may be of any desired number and may be supported
after any suitable plan. They are made by carbonizing thin sheets of paper,
cardboard or other suitable material after the manner employed in forming the
carbon strips of incandescent electric lamps or in any other suitable manner.
Eight sheet clectrodes are shown, a larger number may however be frequently
used with good effects. Owing to the large number of paths afforded by the large
number of contact electrodes, a current of considerable strength may be employed
without deranging the instrument. Instead of employing sheets of carbon thin
sheets of some metal might be used. If metal be employed the opposite electrode
should by preference be of carbon. The nature of the contact owing to the light-
ness of the plates is exceedingly sensitive, and yet the apparatus is perfectly
effective both in the transmission of very loud and very faint sounds.
The invention is not limited to the particular details of construction herein
described and it may be applied in many other different ways. The feature of the
adjustment is not absolutely necessary.
The electrodes G may be mounted in other ways and the electrode with which
they make contact may be of any other desired form. Electrical connection with
the diaphragm electrode from the binding screw O might also be made in other
ways.
So far as that portion of the invention is concerned which consists in mounting a
series of independently pivotted or gravity actuated electrodes upon a common
adjustable support other and old forms of electrodes might be employed in place of
the thin sheets or plates which rest with their edges in contact with the opposite
electrode,
Having now described the nature of the said Invention and in what manner the
same is to be performed I declare that I claim
First. A compound electrode for a telephone transmitter consisting of a number
of simple independently yielding electrodes, in combination with a common
adjustable support for said electrodes, substantially as set forth.
Second A compound electrode for a telephone transmitter consisting of a
number of simple freely pivotted electrodes resting by the action of gravity upon

page_text: the opposite electrode in combination with a common adjustable support upon
which said electrodes are pivotted substantially as set forth.
Third: A compound electrode for a telephono transmitter consisting of a series
of parallel independently pivotted carbon plates fixed upon a common support and
resting with their edges against the opposite electrode substantially as set forth.
Fourth A compound electrode for a telephone transmitter; consisting of a
number of parallel pivotted plates formed of carbonized cardboard, paper, or
equivalent material and resting with their edges against the opposite electrodo
substantially as set forth.
Fifth-The combination of an electrode connected with the diaphragm of a trans-
mitter, and an electrode consisting of a thin pivotted plate resting with its edge
against the first said electrode substantially as set forth.
Sixth: A contact electrodo for a telephone transmitter consisting of a plate of
carbonized cardboard or paper resting with its edgo against the opposite electrodo
substantially as set forth.
Seventh The combination of a compound electrode, consisting of a series of
light pivotted parallel plates, an electrode con nected to a diaphragm against which
electrode the parallel plates bear with inclined edges and an adjustable support for
said pivotted electrodes adjustable to and from the electrode connected with the
diaphragm substantially as set forth.
Eighth-The combination of a series of parallel pivotted plates, a cross bar
connected to a diaphragm against which bar the edges of the pivotted plates rest, a
conducting bar upon which the pivotted plates are strung and supported for said
conducting bar adjustable longitudinally substantially as set forth.
In witness whereof I the said Edward Griffith Brewer have hereunto set
my hand and seal this Twenty first day of July in the year of our Lord
one thousand eight hundred and eighty two.