IMPROVE- MENTS IN TELEPHONES
Year: 1877

page_text: LETTERS PATENT to Carl Heinrich Siemens, of No. 12, Queen Anne's Gate,
Westminster, in the County of Middlesex, for the Invention of " IMPROVE-
MENTS IN TELEPHONES." A communication from abroad by Dr. Ernst Werner
Siemens, of Berlin, in the German Empire.
Sealed the 1st February 1878, and dated the 10th December 1877.
PROVISIONAL SPECIFICATION left by the said Carl Heinrich Siemens at
the Office of the Commissioners of Patents on the 10th December 1877
&
CARL HEINRICH SIEMENS, of No. 12, Queen Anne's Gate, Westminster, in the
County of Middlesex. IMPROVEMENTS IN TELEPHONES." [A communication from
abroad by Dr. Ernst Werner Siemens, of Berlin, in the German Empire.]
In telephones, as usually constructed, in which the vibrations of an iron
diaphragm placed in presence of a coiled magnet induce in the coil currents of
electricity, which being transmitted to the coil of another magnet cause vibrations
of another iron diaphragm in its presence, the diaphragm is in each case strained to
a certain extent out of its natural condition of equilibrium by the attraction of the
adjacent magnet, and consequently its vibrations are so far effected as to impair its
efficiency either in receiving or emitting pulses of sound.
This Invention relates to a method of constructing diaphragm telephones so as
to avoid this defect, either when a diaphragm of thin iron is employed or when a
membrane is used with a magnetic body attached to it, and to a construction of
telephone in which a bell is employed instead of a diaphragm. For this purpose,
according to one construction, the iron diaphragm is fixed in a circular box, each
side of which is a permanently magnetic disc. At the centre of one of these discs
there is a core surrounded by a coil; the other disc on the opposite side of the
sheet has a hole in its centre for the passage of the sound pulses. This disc being
opposite to the other disc and core, the iron diaphragm rests between the two in
equilibrium or without being strained more in the one direction than in the
other.
According to a modified construction the iron diaphragm has on each side of it
a tubular magnet surrounded by a coil, whereby the sheet is kept in balance. The

page_text: magnets being open, tubes give passage for the sound pulses at each side of the
instrument, and several such instruments may be placed one above the other so as
to reinforce the sound pulses produced, or to augment the electric impulses caused
by given sound pulses
When two coils are employed, as above described, in each instrument, they are so
connected to the line wire or wires that the movements of the iron diaphragm in
its vibrations to and from the two magnetic poles produce concurrent electric
impulses, which being transmitted to the receiving instrument produce concurrent
influences on its diaphragm.
Instead of employing an ion diaphragm a sheet of non-magnetic metal or a
membrane may be used in a telephone by attaching to its middle an annular coil,
preferably of aluminium, which projects into an annular space formed between the
magnetic core and a surrounding magnetic disc, the core and the disc having
opposite polarity.
When the sleet or membrane, with the sending instrument, is caused to vibrate
by sound pulses, the vibration of the coil in the magnetic field induces electric
currents, which being transmitted to a corresponding receiving coil at a distance
cause it to vibrate in its magnetic field, and the vibrations of the sheet or membrane
to which the receiving coil is attached produce sound pulses, corresponding with
those at the sending station.
The magnetic discs above mentioned, as well as the tubular magnets, or the core
and disc constituting the annular magnetic field,,may either be of iron or steel,
receiving magnetism by induction.
For the purpose of magnetising them by induction they may be attached to the
poles of a horse-shoe magnet, which bends round from the one side of the instrument
to the other.
A bell may be.en ployed in lieu of a diaphragm by mounting it by a central stem
over a horse-shoe magnet, the poles of which are turned towards the periphery of
the bell and are provided with coils. When one of two bells thus arranged, and
having their magnet coils connected by a line wire or wires, is struck, the other
also is caused to sound.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Carl Heinrich Siemens in the Great Seal Patent Office on the 30th
April 1878.
CARL HEINRICH SIEMENS, of No. 12, Queen Anne's Gate, Westminster, in the
County of Middlesex. "IMPROVEMENTS IN TELEPHONES." A communication from
abroad by Dr. Ernst Werner Siemens, of Berlin, in the German Empire.
In telephones, as usually constructed, in which the vibrations of an iron
diaphragm placed in presence of a coiled magnet induce in the coil currents of
electricity, which being transmitted to the coil of another magnet cause vibrations
of another iron diaphragm in its presence, the diaphragm is in each case strained to
a certain extent out of its natural condition of equilibrium by the attraction of the
adjacent magnet, and consequently its vibrations are so far affected as to impair its
efficiency either in receiving or emitting pulses of sound.
This Invention relates to a method of constructing diaphragm telephones so as
to avoid this defect, either when a diaphragm of thin iron is employed or when a
membrane is used with a magnetic body attached to it, and to a construction of
telephone in which a bell or tuning fork is employed instead of a diaphragm. For
this purpose, according to one construction, the iron diaphragm is fixed in a circular
box, each side of which is a permanently magnetic disc. At the centre of one of
these discs there is a core, surrounded by a coil. The other disc on the opposite
side of the diaphragm has a hole in its centre for the passage of the sound pulses.
This disc being opposite to the other disc and core, the iron diaphragm rests between
the two in equilibrium, or without being strained more in the one direction than in
the other.
According to a modified construction the iron diaphragm has on each side of it
a tubular magnet surrounded by a coil, whereby the sheet is kept in balance. The
magnets being open, tubes give passage for the sound pulses at each side of the
instrument, and several such instruments may be placed one above the other, so as
to reinforce the sound pulses produced, or to augment tho electric impulses caused
by given sound pulses.
When two coils are employed, as above described, in each instrument, they are so
connected to the line wire or wires that the movements of the iron diaphragm in
its vibrations to and from the two inagnetic poles produce concurrent electric
impulses, which being transmitted to the receiving instrument produce concurrent
influences on its diaphragm.
Instead of employing an iron diaphragin a sheet of non-magnetic metal or n
membiane may be used in a telephone by attaching to its middle an annular coil,
preferably of aluminium, which projects into an annular space formed between n
magnetic core and a surrounding magnetic disc, the core and the disc having
opposite polarity.
When the sheet or membrane of the sending instrument is caused to vibrate by
sound pulses, the vibration of the coil in the magnetic field induces electric currents,
which being transmitted to a corresponding receiving coil at a distance cause it to
vibrate in its magnetic field, and the vibrations of the sheet or membrane to which
the receiving coil is attached produce sound pulses, corresponding with those at the
sending station.
The magnetic discs above mentioned, as well as the tubular magnets, or the core
aud disc constituting the annular magnetic field, may either be of iron or steel,
receiving magnetism by induction.
For the purpose of magnetising them by induction they may be attached to the
poles of a horse-shoe magnet, which bends round from the one side of the instru-
ment to the other.
A bell may be employed in lieu of a diaphragm by mounting it by a central stem
over a horse-shoe magnet, the poles of which are turned towards the periphery of
the bell and are provided with coils. When one of two bells thus arranged, and

page_text: having their magnet coils connected by a line wire or wires, is struck, the other
also is caused to sound, and in like manner vibrating bodies, such as tuning forks,
may be employed for telephonic purposes.
DESCRIPTION OF THE DRAWINGS.
Fig. 1 represents one form of telephone according to this Invention. A cylin-
drical magnetic box has its two opposite sides a and b made of hardened steel,
magnetised in such a manner that the one pole is in the centre and the other pole
in the periphery of each, the two centres having opposite polarity. In the centre
of the lower disc a is fixed an iron core c, surrounded by a coil e of insulated wire,
and in the middle of the upper disc b is fixed an iron tube d, surrounded by the
coil e¹. The thin iron sheet fis fastened at the periphery of the box at such distance
from the inner ends of c and d that their attraction acts equally on it, so that in
its position of rest it is not strained to either side.
In the modified construction, represented in Fig. 2, both cores of the coils
have the form of tubes, so that each gives passage to sound pulses. In this case
both discs have similar polarity, like poles facing the iron diaphragm which takes
opposite polarity. The attraction on the diaphragm between the two magnetic
poles is thus completely equalised, whether the diaphragm be at rest or in vibration.
The two tubes perimit passage for the sound, pulses on both sides of the diaphragm,
and these may be communicated to both ears by sound pipes, such as ear
trumpets.
Two or more telephones, constructed as shewn in Fig. 2, may be placed one
upon another to obtain an increase of effect, and in this case the centres of the
diaphragms may be firmly connected to each other by light struts or ties.
For the magnetic core or tube on the one side of the diaphragm may be sub-
stituted coiled polar extensions of a horse-shoe magnet, as shewn in Fig. 2,
where g, g, are iron cores attached to the poles of the magnet M and surrounded
by coils.
By making the cores g flat and thin, so that the coils are long in one dimension
and narrow in the other, as shewn in plan at Fig. 20, the poles are brought
very near to each other, which is of great advantage to the efficacy of tho
telephone.
The same construction may be employed without the upper magnet or disc, as
shewn in Fig. 2b.
•
Fig. 3 represents a construction similar to that shewn in Fig. 1, a horse-shoe
magnet being substituted for the two magnetised discs.
In the modification represented in section at Figure 4, and in front view by
Fig. 4, a much smaller diaphragm is used, it being held between cushions of
india-rubber or other material having elasticity sufficient to permit of the vibration
of the diaphragm.
Instead of an iron diaphragm or a non-magnetic membrane, having on it an iron
disc, non-magnetic membranes may be employed, as shewn in Figs 5 and 6.
In the construction, shewn by Fig. 5, the vibrating diaphragm is a thin sheet
of brass or German silver, to the centre of which is fixed a light coil u, preferably of
aluminium. This coil is in an annular magnetic field produced by a powerful horse-
shoe magnet. When the diaphragm, which is in equilibrium, vibrates, currents are
induced in the coil which moves with it, and these currents conveyed to the distant
station cause a similar coil there to vibrate with its membrane, reproducing the
sound pulses which gave motion to the former coil.
According to the construction shewn by Fig. 6 the coil in the magnetic field is
fastened to a membrane, of parchment or other material of trumpet form, to increase
the effect of the sound pulses.
Telephones, like those shewn in Figs. 5 and 6, without iron diaphragms,
require powerful magnets, but they reproduce articulated sounds with great
distinctness.

page_text: For a telephonic alarum a bell or tuning fork may be employed instead of a
diaphragm.
Fig 7 represents a "sympathetic bell." A is a steel magnet, on one end of
which is fixed a steel bell B; the other end carries two iron cores d, d, surrounded
by wire coils E and E. Between the ends of the cores d, d', is the rim of the bell,
being thus situated between two equally powerful magnetic poles of opposite
polarity to the bell, and therefore equally acted upon from both sides. Two bells
of equal pitch being thus arranged and inserted in the same circuit, the vibration of
the one will cause the other to sound loudly; of bells of different pitch inserted
in the same circuit, only those of the same pitch with the sending bell will be
caused to sound.
Fig. 8 shews a front view, and Fig. 9 a side view of a "sympathetic tuning
fork. A is a steel magnet; B, B, the tuning fork, the stem of which is attached
to the one pole of the magnet. Between the prongs of the tuning fork is the iron
core C, which is fastened to the other pole of the magnet A, and is surrounded by
a wire coil. Outside the prongs of the tuning fork are the iron cores c and c³,
which are fastened to the same pole and also surrounded by coils; each prong of
the tuning fork is thus situated between two equal magnetic poles. The coils being
so connected that a current causes C to have opposite magnetism to c and c², the
prongs are moved alternately inwards and outwards, and sound if the current
impulses correspond in their period with the vibrations of the tuning fork.
The inner core C may be dispensed with, retaining the outer cores c and c², or
these may be dispensed with and the inner coro alone retained; but in these cases
the result is more feeble than when all three cores are employed.
Having thus described the nature of the said Invention, and in what manner the
same is to be performed, as communicated to me by my foreign correspondent, I
claim as improvements in telephones,-
First. Arranging the vibrating diaphragm, so that in its state of rest it is in
equilibrium as to magnetic force acting on it.
Second. The use of a horse-shoe magnet for producing the magnetic field in which
the vibrations take place, substantially as herein described.
Third. The use of annular magnetic poles formed by tubular cores, presenting
passages for sound pulses, substantially as herein described.
Fourth. The use of round magnetic plates, presenting polarity in their centres,
substantially as described.
Fifth. Arranging in face of each other two or more telephones having sound
orifices of the kind referred to in the third claim, for the purpose of increasing the
transmitted sounds, whether the several diaphragms may be connected with each
other or not, substantially as herein described.
Sixth. Arranging the vibrating iron or steel body in metallic contact with the
one pole of a magnet while the core of the electro-magnet is connected to the other
pole, substantially as herein described.
In witness whereof, I, the said Carl Heinrich Siemens, have hereunto set my
hand and seal, this Twenty-seventh day of April, in the year of our Lord
One thousand eight hundred and seventy-eight.
DIATY CYANAIזת זסם