IMPROVEMENTS IN ADDADATIISTELEPHONIC
Year: 1883

page_text: LETTERS PATENT to Horace Hamline Eldred of Queen Victoria Street in the
City of London for an Invention of "IMPROVEMENTS IN
ADDADATIIS
"
TELEPHONIC
PROVISIONAL SPECIFICATION left by the said Horace Hamline Eldred at
the Office of the Commissioners of Patents on the 7th February 1883.
HORACE HAMLINE ELDRED of Queen Victoria Street in the City of London
"IMPROVEMENTS IN TELEPHONIC APPARATUS
"
My Invention relates to telephonic apparatus of the type of what is known as
electro-magnetic telephones and has for its object increasing their efficiency and
facilitating their use and manipulation
In carrying out one part of my Invention, in order to effect these objects I
employ a parchment or membraneous diaphragm secured at its edges, and with a
thin piece of metal capable of inductive action attached to its centre opposite an
electro magnet in the well known manner, but I cover the outer surface of this
parchment or membraneous diaphragm with a disc of mica, brass, or other
equivalent material (that is to say a material not capable of inductive action but
which will prevent the passage of moisture to the diaphragm) the said disc being
either attached or not to the said diaphragm. By this means I overcome the
difficulty which has hitherto been experienced with this type of telephone and
which is due to the expansion of the parchment or other membrane under the
influence of moisture impeding the efficient working of the apparatus, since by my
improvement the ingress or action of moisture is prevented and the normal
operation of the diaphragm is thus ensured. I may dispense with the parchment
or other membrane and employ alone the mica, brass, or equivalent disc, with a
thin piece of metal capable of inductive action at its centre. I may use a tubular
electro-magnet with a diaphragm of the type hereinbefore described or with one
formed of a material capable of inductive action pivotted to the outer rim of the
magnet; and over the tubular magnet with its diaphragm I place a mouth or ear
piece which greatly intensifies the effect. In conjunction with the mouth or
ear piece I provide a case of a circular or other suitable form made to nearly fit

page_text: the parts to be enclosed, and contain them in a small compass, and in a shape
convenient to handle.
The apparatus may be used either as a transmitter or receiver. When used
as a receiver only I may combine a transmitter of the type of what is
known as "Hunning's," or other equivalent transmitter, in the same case with the
receiver.
I may use a local battery for the purpose of magnetizing the core of the
electro-magnet, the said core being provided with two coils one of which forms
part of the main line whilst the other is in the local circuit, in which may also be
placed the transmitter, the coils of the receiver thus acting as an induction coil to
the transmitter A battery of the type of what is known as the silver or
mercury battery or an equivalent battery may conveniently be used for the
purpose, and may if desired be enclosed in the same case with the transmitter and
receiver

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Horace Hamline Eldred in the Great Seal Patent Office on the
3rd August 1883.
HORACE HAMLINE ELDRED, of Queen Victoria Street in the City of London
"IMPROVEMENTS IN TELEPHONIC APPARATUS "
My said Invention relates to telephonic apparatus of the type known as
electro-magnetic, or magneto-electric telephones, and has for its objects increasing
their efficiency, and facilitating their use and manipulation.
In order to effect these objects the Invention is carried out in the manner
hereinafter described reference being had to the several figures on the accompanying
sheet of drawings
«
One part of my said Invention relates to the use as hereinafter particularly
described, of a parchment or membraneous diaphragm (the term membraneous "
being intended to include any material such for example as paper, capable of being
stretched across a carrying body)
Figure 1, of the accompanying drawings represents a longitudinal vertical section
of a telephone constructed according to my said Invention.
a, is a parchment or membraneous diaphragm stretched tightly across and
secured at its edges to a carrier ring b. This diaphragm is provided at its centre
with a thin piece c, of metal (such for example as iron) capable of inductive action,
and at the outer surface of the ring b, is placed a thin disc d, of mica, brass, or
other similar non-magnetic material, that is to say a substance not capable of
inductive action, but which will prevent the passage of moisture to the diaphragm
(or if preferred the said disc may be attached direct to the diaphragm). The
diaphragm proper with its appurtenances as hereinbefore described constituting
together a compound diaphragm is placed in a case e with the central part c. of
the diaphragm opposite the pole of a simple electro-magnet f contained within the
said case, or opposite the poles of an equivalent electro-magnet of any other form
admitting of such an arrangement, and over the diaphragm is placed a mouth or
ear piece which greatly intensifies the effect. The case e is provided with a
flange or annular projection h of a diameter smaller than that of the interior of
the ring b and the mouth or ear piece g is also formed with a flange h¹ the two
exercising pressure upon the diaphragm and gripping it between them in such a
manner as to stretch the parchment or membrane or like material, and secure the
requisite tautness.
Figure 2, illustrates a mode of employing paper as the material of which the
diaphragm proper is made. In this example two discs a, a, of paper are used, a
piece of tin plate or iron c being placed between them. A carrier ring b, is used
as before on which the paper is stuck when wet so as to contract by drying and
thus promote the requisite tautness, a disc d, of mica, brass, or other similar non-
magnetic material being disposed on the outer side of the disc as before so as to
protect the paper against the action of moisture.
As an equivalent for the mica, brass, or other similar non-magnetic material,
I may coat the surface, or surfaces of the diaphragm with a solution of india rubber,
shellac or other waterproof varnish, sufficiently flexible not to crack. In this case
the paper a, may be gripped between two rings b, b¹ as shown in Figure 3, one of
the rings (6) being turned up at its edge, and rolled over the other (b) with the
paper interposed between them.
By the use of a disc, or covering of non-magnetic material on the outside of the
diaphragm of paper, parchment, or other membrane, I overcome the difficulty
which has hitherto been experienced with this type of telephone and which is due
to the expansion of the parchment or other membrane under the influence of
moisture impeding the efficient working of the apparatus, since by my improvement

page_text: the ingress or action of moisture is prevented and the normal operation of the
diaphragm is thus ensured.
I may dispense with the paper, parchment or other membrane and employ alone
the mica brass or equivalent non-magnetic disc d as shown in Figure 4, with a
thin piece c, of metal (such for example as iron) capable of inductive action, at its
centre.
It will be understood that the modifications of diaphragms shown in Figures 2,
3, and 4, are each intended to be applied to a case fitted with a mouth or ear
piece, and enclosing an electro-magnet as in the arrangement illustrated in
Figure 1.
I may use a tubular electro-magnet with a diaphragm of one of the types herein-
before described, or with one formed of a material capable of inductive action, the
diaphragm in the latter case being pivotted to the outer rim of the magnet.
Figure 5, is a longitudinal section of a telephone having a tubular electro-
magnet f, and with a diaphragm a, say of varnished paper, carrying at its centre
a thin piece c. of metal capable of inductive action, the parts being enclosed in a
compact case e, fitted with a mouth or ear piece g.
Figure 6, is a longitudinal section of a telephone of generally similar construction
but with a diaphragm a formed of a material (such for example as iron) capable
of inductive action pivotted or screwed on one side k, to the outer rim of the
tubular magnet.
Apparatus of any one of the types hereinbefore described may be used either
as a transmitter or receiver.
Having now described and particularly ascertained the nature of the said
Invention and the manner in which the same is or may be used or carried into
effect I would observe in conclusion that what I consider to be novel and original
and therefore claim as the Invention secured to me by the hereinbefore in part
recited Letters Patent is :-
First In an electro-magnetic or magnetic telephone, the combination of a
membraneous diaphragm carrying a piece of metal capable of inductive or magnetic
action, and of a disc of thin mica brass or other material, incapable of inductive or
magnetic action, or a waterproof equivalent therefor, substantially as and for the
purpose herein before described.
Second. The general constructions, arrangements, and combinations of parts
constituting telephones, substantially as herein before described with reference to
Figures 1, 2, and 3 of the accompanying drawings
Third. In an electro-magnetic, or magnetic telephone, the employment of a
diaphragm made of mica, brass or other stiff material not requiring to be strained
upon a ring, and incapable of inductive action, having at its centre a thin disc or
piece of iron or other metal capable of inductive action substantially as herein before
described.
Fourth. The general constructions, arrangements, and combinations of parts
constituting telephones substantially as herein before described with reference
respectively to Figures 5, and 6 of the accompanying drawings
In witness whereof I the said Horace Hamline Eldred have to this my
specification set my hand and seal this sixth day of July in the year of our Lord,
one thousand eight hundred and eighty three.
HORACE HAMLINE ELDRED (L.S.)