IMPROVEMENTS IN TELEPHONE TRANSMITTERS
Year: 1883

page_text: LETTERS PATENT to George Leo Anders of Queen Victoria Street, in the
City of London for an Invention of "IMPROVEMENTS IN TELEPHONE
TRANSMITTERS"
PROVISIONAL SPECIFICATION left by the said George Lee Anders at the
Office of the Commissioners of Patents on the 1st November 1883.
"
GEORGE LEE ANDERS of Queen Victoria Street in the City of London
"IMPROVEMENTS IN TELEPHONE TRANSMITTERS"
My invention relates to improvements in telephone transmitters of that class in
which, by variations of contact pressure, the resistance in the circuit is varied.
For effecting the object of my invention I form the contact surfaces of osmium,
or one surface of osmium and one of some other metal such as aluminium. The
properties which render osmium especially suitable for my purpose are great
hardness and infusibility, and sensitiveness to slight variations in pressure. It
will be obvious that these properties are very valuable with respect to the contact
surfaces. The aluminium affords the advantages of lightness with a high
conductivity for heat and electricity, which properties reduce its liability to fusion
at the point of contact. Both materials moreover are free from the defect of
producing a non-conducting or easily fusible coating by exposure to the air or
under the action of the current.
In practising my invention, when I form one electrode of metallic osmium I use
this metal in as compact and smooth a state as possible and form the other
electrode of aluminium; and I arrange the electrodes so that the microphonic
action takes place at the surface of contact between these two materials. But as
the aluminium is sufficiently soft to permit particles of osmium to be readily
united thereto by pressure, I may use the osmium at the tip or point of an
electrode formed of aluminium, and form both electrodes of aluminium, and after
giving them the proper shape and a smooth surface I impress the osmium in the
form of powder or fine grains into the contact surface of one electrode or the
contact surfaces of both electrodes.
Other metals or conducting substances possessing the qualities which render the
aluminium serviceable may be employed in its place for the purposes of my

page_text: I sometimes form the electrodes of aluminium and place between them a small
quantity of powdered or granulated osmium which has been rubbed in a mortar
with aluminium leaf, so that the said leaf is broken up into small particles which
are intimately mixed with the osmium. In this modification of my invention
other motals can be used in place of aluminium to form the electrodes as the
principal part of the microphonic action takes place between the grains of powdered
metals. A small glass or other insulating tube should be added in the last form to
surround the electrodes and retain the powdered material between them.
In this modification of my invention one electrodo may be attached to a
diaphragm or sounding board and the other pressed towards it by its own weight,
or by a spring, or the two electrodes may be set firmly in the ends of a glass tube
with sealing wax or other cement and the whole mounted upon a diaphragm or
sounding board. I sometimes prefer to make the tube airtight and to exhaust or
nearly exhaust the air therefrom.
According to another modification of the said invention I attach ono electrode to
the diaphragm of the transmitter and about its free end I fit a collar or tube of
cork or similar material into the end of which the other electrode is fitted. A
space is left between the two electrodes in which is placed a short cylinder or
button of aluminium, the surfaces of which are prepared by impressing osmium
powder into them. The electrodes should be faced with platinum or other
inoxidizable metal. Instead of impressing the osmium into the aluminium button
I may simply put a small quantity of osmium in the form of powder between the
button and each electrode. The collar of cork must fit tightly enough to enable
the electrode on the diaphragm to support the other parts. An adjusting screw
fitted in the back of the case serves to vary the pressure upon the electrodes.
I prefer to use the above mentioned transmitting instruments in connection
with a local battery and induction coil in a manner well understood but they may
also be used in direct connection with the line circuit especially if the latter is not
very long..

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said George Lee Anders in the Patent Office on the 1st May 1884.
GEORGE LEE ANDERS, of Queen Victoria Street, in the City of London,
"IMPROVEMENTS IN TELEPHONE TRANSMITTERS
"
My invention relates to telephone transmitters of that class wherein there are
electrodes so arranged that variations of their contact pressure will cause variations
of the resistance in the circuit in which the transmitter is included.
The objects of my invention are to increase the efficiency and simplify the
construction of such instruments, and I effect these objects chiefly by the
employment of osmium in the manner hereinaftor described.
The properties which render osmium especially suitable for my purpose are great
hardness and infusibility and sensitiveness to microphonic action.
In some instances I employ, in combination with aluminium, the osmium
because of its high conductivity for heat and electricity, which propertios reduce
its liability to fusion at the points of contact. Both of the above named materials,
moreover, are free from the defect of producing a non-conducting or easily fusiblo
coating by exposure to the air or under the action of the current.
My invention, in some of the forms or arrangements in which I find it may be
advantageously embodied, is illustrated in the accompanying drawing, in which.
Figure 1 is a side view, partly in transverse section, of part of a transmitter
with my invention applied to the same.
Figure 2 is a view showing the parts at the back or inner side of the diaphragm
of the said transmitter.
Figure 3 is a side view, and
Figure 4 a back or interior view of the diaphragm and its adjuncts as arranged
according to a modification of my said invention.
Figures 5 and 6 are sido or edge views, partly in transverse section, illustrating
other modifications of my said invention.
A is the diaphragm, which may be made of any suitable material. B B are the
electrodes, which are preferably formed of any metal not easily oxidized or fused.
One very advantageous manner of carrying my said invention into practice
consists in placing granulated osmium between two discs or pieces forming the
electrodes and enclosed in a tube or sleeve of india-rubber, cork, or other suitable
material, as in the instrument shown in Figures 1 and 2.
In this instrument one of the electrodes B is attached to the centre of the
diaphragm or sound-board by a screw and nut or by other suitable means; the
said electrodes are formed with discs or other pieces which are enclosed in and
kept at the required distanco apart by the tube or sleeve C. The space D between
the said discs or buttons is filled or nearly filled with grains of osmium. The.
conducting wires E are connected with the electrodes B as shown. I may use any
other convenient and suitable holder instead of the tube C. The instrument shown
in Figures 3 and 4 has the above specified parts in duplicate, the outer ends of the
electrodes B being connected by a small bar or plate E¹.
I sometimes place between the said electrodes a small quantity of granulated
osmium intimately mixed with aluminium leaf or foil by rubbing them together.
In this instrument other metals can be used in place of aluminium to form the
electrodes B as the principal part of the microphonic action takes place between
the mixed grains of osmium and aluminium.
In this modification of my invention, in which one electrode is attached to a
diaphragm or sounding board, the other electrode may be pressed towards it by its

page_text: own weight. If desired the two electrodes may be set firmly in the ends of a glass
or other tube with sealing wax or other cement, and the whole mounted upon a
diaphragm or sounding board. I sometimes prefer to make the tube air-tight and
to exhaust, or nearly exhaust, the air therefrom.
According to another modification of the said invention, I attach one electrode
to the diaphragm of the transmitter, and about its free end I fit a collar or tube of
cork or similar material, into the end of which the other electrode is fitted. A
space is left between the two electrodes, in which space is placed a short cylinder
or disc of aluminium the surfaces of which are prepared by impressing grains or
particles of osmium into them. The electrodes should be faced with platinum or
other inoxidizable metal. The collar or tube must fit tightly enough on the
electrodo on the diaphragm to enable the said electrode to support the other parts.
An adjusting screw fitted in the back of the case serves to vary the pressure upon
the electrodes. This form of my instrument is shown in Figure 5. GG are pieces
of aluminium which have the grains of osmium pressed into them and which are
enclosed in the tubes C and between the electrodes B. The two outer or upper
electrodes are connected by the wire or rod H. In the instrument shown in
Figure 6 the pieces G are replaced by granulated osmium at D.
As the aluminium is sufficiently soft to permit particles of osmium to be readily
united thereto by pressure, I sometimes use the osmium at the tip or point of an
electrode formed of aluminium, and I form both electrodes of aluminium and, after
giving them the proper shape and a smooth surface, I impress the osmium in the
form of fine grains into the contact surfaces of the clectrodes.
Although my experiments indicate that the best results are obtained by the uso
of aluminium in the manner described, yet other metals possossing to a greater or
less, degree the qualities which render aluminium serviceable may be employed in
combination with osmium for the purposes of my invention.
I prefer to use the above mentioned transmitting instruments in connection
with a local battery and induction coil in a manner well understood, but they may
also be used in direct connection with the line-circuit.
In describing my invention I have shown instruments.in which a diaphragm is
employed, but it is obvious that my improvements are altogether independent
of the use of a diaphragm and may be used in connection with any vibrating
body.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is: :-
First: In a telephone transmitter, the employment of granulated osmium
between two electrodes such as B in the drawing for the purposes above
specified.
'
Second-The modification of my invention wherein I use a piece of aluminium
which has grains of osmium incorporated therewith, substantially as set forth.
Third-The improved transmitter constructed as above described and as
illustrated in the accompanying drawing.
In witness whereof I- the said George Lee Anders have hereunto get my hand
and seal this twenty fifth day of April in the year of our Lord One thousand
eight hundred and eighty four.