AN IMPROVED MEANS OF TRANSMITTING SOUND BY MEANS OF ELECTRICITY AND OF REPRODUCING THE SAME AT A DISTANT STATION
Year: 1884

page_text: We FRANK VILLIERS-STEAD of No 50 Lombard Street in the City of London
Electrical Agent and ELWARD RADFORD HEDGMAN of N° 64 Palma Crescent
Lavender Sweep Wandsworth in the County of Surrey Electrician do hereby
declare the nature of the said invention for AN IMPROVED MEANS OF TRANSMITTING
SOUND BY MEANS OF ELECTRICITY AND OF REPRODUCING THE SAME AT A DISTANT
STATION to be as follows:-
The said invention consists of 2 parts namely (1.) a direct acting multiple plate
transmitter and (2) of the magnetic arrangements suitable for use in a Receiver.
The transmitter consists of a series of flat plates of Carbon of suitable width and
thickness supported by means of projecting shoulders resting loosely in two upright
pillars or blocks of Carbon supported in or on a nonconductive frame or stand being
in circuit with a battery and primary wire of an induction coil in the usual
manner-We entirely dispense with any diaphragm or "tympan "and no box is
necessary although for the purposes of protection from accidental injury it may be
enclosed in a case of any convenient shape-The plates have one broad or two or
more narrow shoulders at each end by which they rest loosely in holes or grooves
in the pillars or are connected with the pillars by pins or projections of Carbon
affixed to or cut out of the pillars and inserted into or bearing the plates. The
plates are attached in such a way that the adjacent edges shall not be in contact
with each other but must overlap by having their edges bevilled off on opposite
sides as per drawing Figure 1 or they may be arranged in an imbricated manner
that is to say as the lathes of a Venetian Blind. The Fig 1 in the annexed
drawing shews the principle of the said transmitter.
We claim that the transmitter requires neither Case, diaphragm or "tympam."
The magnetic arrangement suitable for use in a receiver consists of a soft iron
armature Fig 24 surrounded by insulated copper wire wound on a bobbin which
by preference is made of soft iron but may be of any other suitable material and
which is inserted between and very close to the opposite poles of a permanent

page_text: magnet (in the manner shewn in the figure) having soft iron pole pieces B. The
permanent magnet may be replaced by an Electro magnet in which case soft iron
pole pieces are not necessary.
If a current of Electricity from the transmitter be sent through the said coil
surrounding the armature the amount of magnetism passing through the armature
will be varied in a manner corresponding with the undulations in the current
passing through the coil. At the same time the amount of magnetism free to act
upon a diaphragm tongue or other body capable of magnetic influence would be
varied in a proportionate ratio thus producing vibrations in harmony with those of
the Electrical modulations set up in the current.
Dated this 2nd day of Mob 1001
F. VILLIERS-STEAD.
E. R. HEDGMAN.

page_text: We, FRANK VILLIERS-STEAD of Number 50, Lombard Street in the City of
London Electrical Agent and ELWARD RADFORD HEDGMAN of Number 64 Palma
Crescent, Lavendar Sweep Wandsworth in the County of Surrey Electrician
do hereby declare the nature of our invention for AN IMPROVED MEANS OF
TRANSMITTING SOUND BY MEANS OF ELECTRICITY AND OF REPRODUCING THE
SAME AT A DISTANT STATION, and in what manner the same is to be performed to
be particularly described and ascertained in and by the following statement:―
TAS
This invention consists of two part namely (1) à direct acting plate transmitter
and (2) of the magnetic arrangement suitable. for use in a receiver in conjunction
with a diaphragm which latter is not patented.
(1.) The transmitter consists of a series of flat plates or bars of Carbon
(preferably of highly compressed fine grained Carbon) supported by means of
projecting shoulders which rest loosely in two upright pillars or blocks of Carbon
supported in or attached to a nonconductive frame or stand being in circuit with a
battery in the usual manner.
By experiment we find that plates of the thickness of 2 millimetres and two
and a half inches long by three quarters of an inch wide are convenient sizes; an 1
that for practical purposes, not more than three plates are necessary although the
transmitter will speak, but not so well, with two plates, or even a single plate:
We entirely dispense with any diaphragm and although for the purpose of pro-
tection from accidental injury the transmitter may be enclosed in a case, it is not
essential to the action of the apparatus that the transmitter should be so enclosed.
The plates are connected with the pillars by shoulders projecting from the plates
and inserted into holes or grooves in the pillars or by pins or other projection from
the pillars fitting into holes in the ends of the plates.
The most economical method of attaching these plates to the pillars, is that
shewn in the drawings which accompany this specification videlicit; three grooves
are made in a piece of Carbon which forms part of a pillar of a width a little
larger than the width of the shoulders of the plates, and of a depth a little greater
than the thickness of the plates it being essential that the plates shall fit loosely
to the pillars, the plates rest in these grooves and another piece of Carbon, of the
same length and width as the piece first mentioned, is screwed down over this piece,
and so the plates are kept in position.
It is not only essential that the plates should fit loosely to the pillars, but also
that while the edges of the plates are close together, they should not touch each
other They may overlap each other in an imbricated manner, but we prefer that
the opposed edges should be bevilled off in the manner shewn in Figure 4.
We find, by experiment, that while this transmitter is effective in whatever
position it be placed, the best results are obtained if the upper part be somewhat
inclined towards the speaker, but the amount of inclination depends upon the
thickness of the plates and quality of the Carbon used.
Sound waves impinging on the plates of Carbon produce variations in the
current passing through the wire in the circuit of which they are placed.
Figure 1 is an elevation of the transmitter with the inner portion of the
pillar (E Figure 2) removed to shew the way in which the grooves are cut in the
outer portion of the pillar d, the plates are lettered a, b and C, the grooves are
lettered h. i. k the conducting wires f and g are attached, in the usual manner, to
the pillars E and are in circuit with the Battery.
We prefer however that the transmitter should be connected with the primary
wire of an induction coil,

page_text: Figure 3 is the same with the inner portion of the plate placed in position, the
whole being screwed together and affixed to the support by the screws as shewn.
Figure 2 is a sectional view of figure 1 shewing the mode in which the whole
is attached to the case a portion of which only is shewn lettered h, d and c are
respectively the outer and inner portion of the pillar and a, b and c are the plates.
Figure 4 is an enlarged sectional view shewing the arrangement of the plates
with the edges bevilled.
(2) Our invention of the magnetic arrangement suitable for use in a receiver
consists of a soft iron armature inserted between and very close to (but not
touching) the opposed poles of a horseshoe magnet or a combination of bar magnets
as shewn in the Figure. The armature is surrounded by insulated Copper wire
wound round a bobbin. Affixed to the ends of the magnet are soft iron pole
pieces.
Figure 1 shews an elevation of the apparatus a¹ all form the compound magnet
and consist. of four bar magnets fastened at one end to a soft iron block b and kept
rigid by a further block of brass or some other nonmagnetic substance fixed in the
position of c in the figures; d is the bobbin, the armature is not shewn in this
figure being within the bobbin, but is shewn at h in the sectional view, figura 2.
To the ends of the outer magnets a¹ are attached the soft iron pole pieces f. In
the position indicated by the line y is placed a membraneous diaphragm with a
plate of soft iron fastened to the centre or tongue of soft iron, but no claim is
made to the use or construction of a diaphragm or tongue as forming any part of
our invention.
Figure 2 is a sectional view of the same instrument shewing E, the ends of the
bobbin; the soft iron armature; d the coil of, insulated Copper wire; the other
letters as in Figure 1.
Figure 3 is the elevation at right angles to Figure 1. E, being the ends of the
bobbin the pole piece; and a¹ all the compound magnet. The compound.
permanent magnet may be replaced by an electro magnet in which case the soft
iron pole pieces are unnecessary.
The pole pieces may be affixed in such a manner that the poles are at right angles
to the axis of the magnet.
The whole arrangement with a suitable diaphragm or tongue is enclosed in such
a case as can be conveniently held to the ear.
We prefer that the terminal ends of the coil & Figure 2 should be in a closed
circuit with the secondary wire of an induction coil the primary wire of which is
in circuit with the transmitter, but the transmitter and receiver may also be used
together in a simple circuit with a battery.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed, we declare that what
we claim is
1. The use in a telephone transmitter of bars or plates of carbon attached to
pillars or blocks of carbon and without a diaphragm, substantially as herein
described.
2: The use in a telephone receiver of a magnetic arrangement substantially as
herein described and shewn in Figures 1. 2. and 3 of the drawings relating, thereto.
Dated this 3rd day of December 1884.
F. VILLIERS-STEAD.
E. R. HEDGMAN.