IMPROVEMENTS IN TELEPHONIC OR MICROPHONIC APPARATUS
Year: 1883

page_text: LETTERS PATENT to Henry Harris Lake, of the firm of Haseltine, Lake,
and Co, Patent Agents, Southampton Buildings London, for an Invention of
* IMPROVEMENTS IN TELEPHONIC OR MICROPHONIC APPARATUS" communicated
to him from abroad by Joseph Berliner, of Hanover, in the Empire of
Germany
PROVISIONAL SPECIFICATION left by the said Henry Harris Lake at the
Office of the Commissioners of Patents on the 19th November 1883.
HENRY HARRIS LAKE, of the firm of Haseltine, Lake, and Co, Patent Agents,
Southampton Buildings, London, "IMPROVEMENTS IN TELEPHONIC OR MICRO-
PHONIC APPARATUS" [A communication to him from abroad by Joseph Berliner,
of Hanover, in the Empire of Germany]
This invention relates to telephonic or microphonic apparatus and comprises the
employment of a powder which is a conductor of electricity and which is used
under pressure as hereinafter described
In carrying the said invention into practice I provide a speaking tube which is
wound around a drum and one end of which is placed in a metallic bush. A brass
disc in which this bush is fitted is connected by means of screws with another disc
of insulating material, and between the said discs is inserted a perforated plate
covered with a thin sheet or blade of platinum. This platinum blade serves as a
rest or support for the powder which consists of small conducting particles such, for
instance as graphite or iron filings. Upon this powder rests a disc or weight the
underside of which is also covered with a sheet or blade of platinum whilst its
periphery is surrounded with cotton wool. This disc or weight carries a small rod
which is connected by means of a conducting band or strip (of gold for example)
with an attachment screw. This attachment screw rests upon a plate of insulating
material and is connected at its underside with a conducting wire which leads to
one of the wires of an induction-coil..
A wire fastened to another attachment screw leads to the battery. The current
passes to the first named attachment screw through the above mentioned conducting
band or strip and the rod and-through the conducting. powder, the perforated plate,

page_text: and the brass disc, and leaves through the wire connected with the last named
attachment screw.
When a person speaks into the speaking tube the sound waves are propagated
through the apertures of the perforated plate to the thin sheet or blade of platinum
lying thereon, and exert a greater or less pressure upon the loose conducting
particles of the powder thereby causing an increase or decrease in the intensity of
the current.
SPECIFICATION in pursuance of the conditions or
the Letters I atenu
by the said Henry Harris Lake in the Patent Office on the 19th May 1884.
"
HENRY HARRIS LAKE, of the firm of Haseltine, Lake, and Co, Patent Agents,
Southampton Buildings, London, 'IMPROVEMENTS IN TELEPHONIC OR MICRO-
PHONIC APPARATUS" A communication to me from abroad by Joseph Berliner, of
Hanover in the Empire of Germany
This invention relates to telephonic or microphonic apparatus wherein pulverized
or granulated material which is a conductor of electricity is used under pressure, 1
either in a dry state or moistened with water or other liquid, as hereinafter
set forth.
In the accompanying drawing,
Figure 1 is a side elevation, and
Figure 2 a plan of one form or modification of my improved apparatus.
and
Figure 3 is a vertical central section, with some of the parts shown in elevation,
Figure 4 a plan, both drawn to an enlarged scale, of part of the said apparatus.
Figure 5 is a vertical central section of another form or modification of my
apparatus, and
Figure 6 is a plan, and
c
Figure 7 a vertical central section, with some of the parts removed and with some
of the parts shewn in elevation, illustrating a further modification of the said
apparatus.
Like letters indicate corresponding parts throughout the drawing.
I will rst describe the apparatus shewn in Figures 1 to 4. In this 'apparatus,
I provide a speaking tube a which is made of flexible material so that it can be
wound around a drum b. One end of this tube is fixed in a metallic bush or
sleeve c.
This bush or sleeve is screwed, or otherwise fitted, into a disc d of brass
or other suitab e material connected by means of screws d' with a ring e of insulating
material. Between the said disc and ring is inserted a perforated plate covered
with a thin sheet of platinum. This platinum serves as a rest or support for the
aforesaid pulverized or granulated material, which must be a conductor of electricity
such as graphite, iron filings or the like, and which is contained in the chamber or
cavity g. Upon this pulverized or granulated material rests a disc or weight h the
underside of which is also covered with a sheet of platinum, whilst its periphery is
surrounded with cotton wool. This disc or weight, h carries a small rod h' connected

page_text: by means of a conducting band or strip h³ (of gold for example) with an attachment
screw. This attachment screw is fixed to a bar or platej of insulating material
and is connected at its lower end with the conducting wire k which is secured to
one of the wires of an induction-coil &, Figures 1 and 2. Another conducting wire m!
extends from the attachment screw m to a suitable battery.
The current enters by the attachment screw ȧ and passes thence through the
conducting band or strip h³, the rod h¹, the conducting material at g, the perforated
plate and the brass or other disc d, and leaves through the wire m³ connected
with the attachment screw m.
When a person speaks into the tube a, the sound-waves are propagated through
the apertures of the perforated plate f to the thin sheet of platinum lying thereon,
and exert a greater or less pressure upon the loose conducting particles contained
in the space g, thereby causing variations or fluctuations in the resistance to the
passage of the current through the instrument.
The wire connections are shewn in Figure 2.
As the weight h is capable of moving freely up and down, it will respond to and
increase the effect of any vibratory impulses which may be imparted to it through
the medium of the conducting mass at.g.
In the form or modification of my apparatus shewn in Figure 5, the tube or
mouth-piece a is made with a flange a¹ which is fixed to a hollow block or tube n
of vulcanite or other suitable insulating material, closed at the bottom by a metal
diaphragm f'. To the centre of this diaphragm is secured the metal or carbon
block o. In the chamber or cavity g within the tube n is placed a mass of loose
conducting particles such as crushed coke, iron filings, or the like., A metal
weight h rests loosely upon this conducting mass, and to this weight is attached
the metal rod h¹. This rod passes through a hole h³ in the bar or plate j, which is
of insulating material, and the said rod is free to move up and down. Upon the
said bar or plate jis placed an annular trough p which surrounds the rod h¹ and
which is filled, or partially filled, with mercury. Two wires q, q, are soldered, or
otherwise fixed, to the rod h¹, and dip into the mercury in the trough p. The
conducting wire kis fixed to the mercury-trough p and the conducting wire 'm' is
attached to the diaphragm f¹. It will, therefore, be seen that the mercury serves
as a movable contact, that is to say, it effectually maintains the electrical connection
between the rod h¹ and the conductor k, whilst permitting the requisite movement
of the said rod.
It has been ascertained by experiment that.certain beneficial results are obtained,
in transmitters constructed as above described, when the pulverized or granulated
material, instead of being used in a dry state, is moistened with some liquid of
comparatively low electrical conductivity so as to form a moist mass, resembling,
and of the consistency of, sand when sufficiently moistened to cause the particles to
cohere. By employing the said pulverized or granulated material in this state, the
articulation of the sounds transmitted by the instrument is greatly improved, and,
furthermore, the particles being mechanically united have a comparatively slight
tendency to escape from the cavity or space in which they are placed. I therefore
make a mechanical mixture of small particles of carbon, such as lamp-black,
granulated coke, or other suitable conducting material, with water or other liquid
of comparatively low specific conductivity.
The modification of my apparatus shewn in Figures 6 and 7 is designed to adapt
it for use with a moistened mass of such conducting material. In this form of
apparatus, the weight h is made with a peripheral groove at h* which is loosely
packed with felt or similar soft substance, so that the weight can work freely in
the cavity in which the conducting mass is deposited, without any undue friction
against the walls of the said cavity. A metal diaphragm f' is placed at the
bottom of the space g and is preferably surmounted by a sheet of platinum. This
diaphragm is kept in place by the disc d which is fixed to the non-conducting
ring e so as to compress the edge of the diaphragm between itself and the lower
surface of the said ring.

page_text: The aforesaid mixture, when formed into a loosely adhering moist mass and
placed in the cavity or chamber between the weight and the diaphragm, produces
unusually clear articulations, and the homogeneousness of the mass prevents the
escape of the particles thereof which would otherwise be liable to occur.
Having thus fully described the said invention as communicated to me by my
foreign Correspondent, and the manner of performing the same, I wish it
understood that I am fully aware of the fact that the utilization of carbon and
other materials for varying the resistance in telephones and microphones is well
known; I therefore limit my claims to the novel features hereinabove specified,
that is to say, I claim :-
First. In a telephone transmitter or microphone, the employment of a mass of
loose particles of conducting material enclosed in a chamber or cavity and arranged
in combination with, and between, a diaphragm or equivalent part and a movable
weight, substantially as, and for the purpose; set forth.
Second. In a telephone transmitter or microphone, the combination, with the
mass of loose conducting particles and the disc or weight resting thereon, of the
perforated plate covered with a sheet of platinum and held by, and between, a ring
of insulating material and a disc of conducting material, substantially as, and for
the purpose, set forth.
Third. In my improved telephone transmitter or microphone, the combination,
with the weight and rod, of the trough containing mercury to serve as a movable
contact, substantially as described with reference to Figure 5 of the drawing.
Fourth. In a telephone transmitter or microphone, the combination of the
diaphragm, the weight (with or without the packing) and the non-conducting ring
arranged to form a chamber in which is placed a variable resistance consisting of
a moist conducting mass of carbon or similar material, substantially as described
with reference to Figures 6 and 7 of the drawing for the purpose specified.
In witness whereof I the said Henry Harris Lake have hereunto set my hand
and seal this Nineteenth day of May in the year of Our Lord One thousand eight
hundred and eighty four.
HENDV LAKE (10)