IMPROVEMENTS IN ELECTRIC TELEPHONIC APPARATUS
Year: 1878

page_text: LETTERS PATENT to Alexander Graham Bell, of 115, Cannon Street, in the
City of London, Gentleman, for the Invention of "IMPROVEMENTS IN ELECTRIC
TELEPHONIC APPARATUS."
ealed the 6th August 1878, and dated the 14th February 1878.
PROVISIONAL SPECIFICATION left by the said Alexander Graham Bell at
the Office of the Commissioners of Patents on the 14th February 1878.
ALEXANDER GRAHAM BELL, of 115, Cannon Street, in the City of London,
Gentleman. "IMPROVEMENTS IN ELECTRIC TELEPHONIC APPARATUS.'
This Invention of improvements in electric telephonic apparatus is an improve-
ment upon the electric telephone as invented by me, in the which a straight rod of
iron or steel with a coil round one end is employed, the rod being a permanent
magnet or rendered magnetic by a battery, and in which the plate armature is
attached to a block of wood, and has in connection with it a speaking or hearing
tube.
My present improvements consist in the employment of a tubular magnet in
place of the solid rod heretofore employed, and in attaching the plate to that pole
of the magnet which has formerly been unused.
Figure 1 shows a vertical section of one form of tubular magnet telephone in
which N, S, is the tubular magnet, which can be used in place of the hearing or
speaking tube previously employed, and which also serves as a handle, by means of
which the telephone can be lifted to the mouth or ear as required. B is the plate
of iron which can be vibrated in front of the pole S of the magnet; D is a wooden
support to which the plate B is affixed; and a coil of insulated wire.
Figure 2 shows another form of tubular magnet telephone in which the plate B
is attached to the pole N of the tubular magnet N, S, and is free to vibrate in the
neighbourhood of the pole S.

page_text: The tubular magnet may be constructed of iron, or steel, or of any substance
capable of forming a magnet, and may be either permanently magnetised or
magnetised by the influence of a battery current.
It will be understood also that the shape of the magnet may be varied in a variety
of ways; for instance the tubular magnet may be flattened as in Figure 3, or
lengthened as in Figure 4.
Figure 3 represents a portable form of telephone somewhat similar in shape to a
watch which can be carried in the pocket for testing purposes.
Figure 5 is a perspective view of the same form of apparatus composed of a
compound tubular magnet made in sections.
The coil E may also be varied in construction; for instance it may be flat and
short, as in Figure 1; or it may be lengthened, as in Figure 2; or it may fill up
the whole interior of the telephone, as in Figures 3, 4, and 5.
My improvements also consist in making the plate armature from a portion of the
magnet; that is, in so producing a portion of the magnet that it will act as the
vibrating plate; for instance, in Figure 3 each magnet at N is produced inwards to
B, leaving a central aperture at B. The ends of each of these projections may be
attached to a metal ring.
My improvements also consist in attaching the coil itself to the vibrating plate so
as to let the coil project from the plate, and then in this recess I place the end of the
rod magnet; in this case the plate and attached coil vibrating before the pole of the
magnet, which form of apparatus may be applied to either of the apparatus shown,
as well as to the one just described without Drawings.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Alexander Graham Bell in the Great Seal Patent Office on the 7th
August 1878.
ALEXANDER GRAHAM BELL, of 115, Cannon Street, in the City of London,
Gentleman. "IMPROVEMENTS IN ELECTRIC TELEPHONIC APPARATUS."
This Invention of improvements in electric telephonic apparatus is an improve-
ment upon the electric telephone as invented by me, in the which a straight rod of
iron or steel with a coil round one end is employed, the rod being a permanent
magnet or rendered magnetic by a battery, and in which the plate armature is
attached to a block of wood, and has in connection with it a speaking or hearing
tube.
My present improvements consist in the employment of a tubular magnet in
place of the solid rod heretofore employed, and in attaching the plate to that pole
of the magnet which has formerly been unused.
Figure 1 shows a vertical section of one form of tubular magnet telephone in
which N, S, is the tubular magnet, which can be used in place of the hearing or
speaking tube previously employed, and which also serves as a handle, by means of
which the telephone can be lifted to the mouth or ear as required. B is the plate
of iron which can be vibrated in front of the pole S of the magnet; D is a wooden
support to which the plate B is affixed; and E, a coil of insulated wire.
Figure 2 shows another form of tubular magnet telephone in which the plate B
is attached to the pole N of the tubular magnet N, S, and is free to vibrate in the
neighbourhood of the pole S.
The tubular magnets may be constructed of iron, or steel, or of any substance
capable of forming a magnet, and may be either permanently magnetised or mag-
netised by the influence of a battery current.
It will be understood also that the shape of the magnet may be varied in a variety
of ways; for instance, the tubular magnet may be flattened as in Figure 3, or
lengthened as in Figure 4.
Figure 3 represents a portable form of telephone somewhat similar in shape to a
watch, which can be carried in the pocket for testing purposes.
Figure 5 is a perspective view of the same form of apparatus composed of a
compound tubular magnet made in sections.
The coil E may also be varied in construction; for instance it may be flat and
short, as in Figure 1; or it may be lengthened, as in Figure 2; or it may fill up
the whole interior of the telephone, as in Figures 3, 4, and 5.
My improvements also consist in making the plate armature from a portion of the
magnet; that is, in so producing a portion of the magnet that it will act as the
vibrating plate; for instance, in Figure 3 each magnet at N is produced inwards to
B, leaving a central aperture at B, the ends of each of these projections may be
attached to a metal ring or to a small plate covering the aperture.
My improvements also consist in attaching the coil itself to this vibrating plate,
so as to let the coil and plate vibrate together; which improvement may be applied
to any form of telephone that I have described.
Having described my Invention, what I claim and desire to protect by Letters
Patent is as follows:-
First. In an electric telephone the combination of a tubular magnet with a plate
of iron, or steel, or other material capable of inductive action, substantially as set
forth.
Second. In an electric telephone the combination of a plate of iron or other
material capable of inductive action with a tubular magnet, so that the plate of
iron is in contact with one pole of the tubular magnet, and is free to vibrate in the
neighbourhood of the other pole, the whole for operation, substantially as herein
shown and described.

page_text: Third. In an electric telephone, substantially as herein shown and described, a
tubular magnet for use as a speaking or hearing tube for the purpose of conveying
sounds to or from the plate.
Fourth. In an electric telephone the combination with a tubular magnet and
metal plate of a coil of insulated wire completely filling the interior of the telephone,
substantially as herein shown and described.
Fifth. In an electric telephone a compound tubular magnet, substantially as
herein shown and described.
In witness whereof, I, the said Alexander Graham Bell, have hereunto set
my hand and seal, this Twenty-ninth day of July, in the year of our Lord
One thousand eight hundred and seventy-eight.
VANDED CD ATTAM DETT
מזרעAr
DATTAM DELT
DERR
GRAHAM
(1.C.)