Magneto-Telephonic appar
Year: 1886

page_text: I, FRED HARVEY BROWN of 39 Broadway, New York City, in the County of
New York, State of New York, U.S.A., Electrician, do hereby declare the nature
of this invention and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement :-
My invention relates to an improvement in Magneto-Telephonic apparatus and
it consists in the improved apparatus for transmitting vocal and other sounds, by
disturbing the magnetic tensions of a permanent magnet by vibrating a diaphagin
over its poles and thereby causing electrical pulsations in the helices of wire wound
around the poles of said magnet, which pulsations are reproduced in the helix or
helices of another magnet similarly-connected in circuit, and disturb the magnetic
tensions in the receiving magnet and cause the diaphragm of this magnet to be
deflected in harmonious vibrations with the disturbing diaphragm, the number of
convolutions of wire in the transmitting instrument being greater than in the
receiving instrument.
My invention further consists in a magneto-telephonic system, in which the
magneto-transmitting telephone has a magnetic field of greater intensity than
that of its companion receiving telephone, the said magnetic field varying in
intensity in approximately the same proportion as the resistance between the said
instruments.
My invention further consists in the peculiar construction and combination of
devices that will be set forth more fully hereinafter and particularly pointed out
in the claims.
In the accompanying drawings
Figure 1 is a diagram representing a pair of my improved telephones connected
in circuit.
Figure 2 is an elevation, partly in section of the transmitter.
Figure 3 is a similar view of the receiving instrument.
The object of my invention is to provide an apparatus capable of transmitting
and reproducing articulate speech and other sounds without the use of a battery
current.

page_text: A, represents the transmitting telephone in which B is an enclosing case, which
is composed of wood or hard rubber, or other preferred material, and is provided
with a mouth-piece C.
To the lower side of this case on its inner side, is secured a permanent magnet,
which is composed of the straight magnetized bar a one end of which extends out
through and beyond the side of the case and forms a handle to the instrument.
S represents one pole of the bar and N the opposite pole thereof. To the extreme
N end of the bar a is attached the S end of a magnetized arm b which arm is
arranged directly in the centre of the enclosing case. A similar magnetized arm b
is secured to the bar at one side of the enclosing case, and parallel to arm b the
S end of arm b¹ being also attached to the bar a.
The arms b b¹ with that portion of the bar a between them form a permanent
U-shaped magnet, having terminals of the same polarity.
Helices of insulated wire D are wound around the parallel arms of the magnet,
the arms being wound either both in the same direction or in diverse directions.
This construction of magnet gives it great intensity and energy. The arm b
forms a pole of much greater intensity than the arm 6' but the latter is sufficiently
powerful.
E represents the diaphragm which is connected magnetically with one of the
parallel arms of the magnet, and is thereby magnetized and the centre of the
diaphragm is directly over and out of contact with the terminal end of the other
parallel arm.
The receiving instrument Z is similar in construction to the transmitting tele-
phone, with the exception that the helix or helices of the former have a smaller
number of convolutions of wire than the helix or helices of the transmitting
instrument.
As shown at F in figure 1. only the arm of the magnet in the center of the
enclosing case is provided with a helix of wire in order to render the difference in
the number of convolutions in the transmitting and receiving instruments apparent
at a glance.
The operation of my invention is as follows;-
When a person speaks into the mouth piece of the transmitting instrument the
diaphragm is caused to vibrate, and induces currents of electricity in the helices
which are transmitted to the helix of the receiving instrument and influence the
receiving magnet to cause the diaphragm to vibrate in consonance with the trans-
nitting diaphragm, and thus convey to the ears of the listener the sounds or words
delivered into the transmitting instrument.
In order to utilize all the energy of the magnet my diaphragm is connected
magnetically to the weaker of the parallel similar poles and its centre vibrates
over the other similar pole. The centre of the diaphragm vibrates out of contact
with the terminal arm of the magnet.
The amplitude of vibration is much less, or almost nothing at the edge of the
diaphragm but is in consonance with the centre thereof the difference being only
one of degree which is compensated for by attaching the diaphragm at its edge
directly in magnetic contact with the weaker of the similar poles of the magnet.
Although the deflection of the diaphragm is less at the edge than at the centre,
the electrical disturbance is rendered equal at this point to the disturbance at the
centre by reason of attaching the edge of the diaphragm directly to the weaker
pole, thus intensifying the magnetic field in which the disturbance takes place.
Heretofore it has been the common practice to make the receiving and trans-
mitting instruments of this class interchangeable, that is to say, that both are
equipped with helices having the same number of convolutions.
My invention differs from that in that I provide my transmitting telephone
with a greater number of convolutions of wire than the receiving instrument,
thus increasing the intensity of the magnetic field because convolutions of wire are
☐

page_text: immersed therein. A larger area of the magnetic field is also intercepted by the
wires and consequently a higher electro-motive force and a greater quantity of
current are by this means obtained, which latter expression is equivalent to a
greater intensity of current, this intensity of current being increased proportional
to the resistance of the circuit.
From tests that I have made I have arrived at the following to give the best
results.
For a short distance telephone, to be used through a circuit having a resistance
of from five to forty Ohms I first construct a receiving instrument having just
a sufficient number of convolutions in its helix or helices to increase and diminish
the complete saturation of the magnet, and produce a sufficiently intense magnetic
attraction and repulsion of its diaphragm to satisfactorily re-produce speech.
The instrument is then tested by trying it in circuit with transmitters having
successively less and less intensity of current, until I reach a limit beyond which
an additional diminution of the intensity of the current in the transmitter no
longer reproduces speech with the maximum distinctness. I then determine
whether the receiver has more convolutions than necessary. If it has the
superfluous resistance in its helix or helices and its additional coercive force render
it less sensative to the rapidly alternating currents of the transmitter, I therefore
proceed to un-wind convolutions from the receiver and if it re-produces speech
more satisfactorily I continue to unwind until the maximum efficiency is obtained.
Having finished the receiver I construct the transmitter with constant reference
thereto. The receiver already made operates with a given intensity of current.
If its diaphragm were in like manner mechanically vibrated by the voice, it would
produce a current of like intensity but this intensity is not sufficient to traverse
the resistance of the circuit, plus the resistance of the helix or helices of another
receiver and have strength enough left to vibrate its diaphragm so as to reproduce
speech with maximum distinctness. For this reason I give to the transmitter
more convolutions than the receiver, and this must be experimentally determined
with each instrument made. I connect the receivers in a circuit say of forty Ohms
resistance and starting with a receiver for a transmitter I add convolutions to its
helices until speech is reproduced with maximum distinctness.
In the above mentioned current of forty Ohms resistance, I find that if the
receiver has a length of wire corresponding to forty Ohms of No 36 copper the
transmitter will attain maximum results when it has a number of convolutions
corresponding to one hundred and twentyfive Ohms of the same size wire.
This varies in each instrument because no two magnets can be made having the
same magnetic moments or the same degree of saturation or even exactly the same
quality of steel indeed the resistance of even the wire that forms the helices varies.
If it is to be used over a circuit of ten thousand Ohms, I find that the
transmitter works better if a little more wire is added to it which is approximately
one-half an Ohm of wire for every additional one hundred to five hundred Ohms
resistance of circuit, the exact amount being determined by experimental test.
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
J claim is
1.) The combination with a transmitting instrument having a permanent magnet,
helices wound around the magnet, and a diaphragm arranged in proximity to the
poles of the magnet, of a receiving instrument of similar construction, connected
in circuit with the transmitting instrument the number of convolutions of wire
in the transmitting instrument being greater than in the receiving instrument
substantially as described.
2.) A permanent magnet having parallel terminal arms of the same polarity,
and the extended arin of opposite polarity, which extended arm increases the
magnetic intensity in the parallel arms, substantially as described.

page_text: 3.) The permanent magnet having parallel terminal arms of the same polarity,
and the extended arm of opposite polarity, in combination with the diaphragm
secured to one of the parallel arms and free to vibrate over the other, and a helix
on one or each of the parallel arms substantially as described.
4.) In a magneto-telephonic system a magneto transmitting telephone having
a magnetic field of greater intensity than that of its companion magneto receiving
telephone, the said field varying in intensity in approximately the same proportion
as the resistance between the said instruments.