AN IMPROVEMENT IN THE RECEIVING INSTRUMENT OF SPEAKING TELE- PHONES ted
Year: 1883

page_text: LETTERS PATENT to Herbert John Allison, of the firm of Allison Brothers,
Patent Agents, of Southampton Buildings, London for an Invention of
"AN IMPROVEMENT IN THE RECEIVING INSTRUMENT OF SPEAKING TELE-
PHONES communicated to him from abroad by James Hart Robertson,
of Brooklyn, New York, United States of America,
"
PROVISIONAL SPECIFICATION left by the said Herbert John Allison at
the Office of the Commissioners of Patents on the 6th November 1883.
HERBERT JOHN ALLISON, of the firm of Allison Brothers, Patent Agents,
of Southampton Buildings, London, AN IMPROVEMENT IN THE RECEIVING
INSTRUMENT OF SPEAKING TELEPHONES a communication, to me from abroad
by James Hart Robertson, of Brooklyn, New York, United States of America,
"
My invention relates to a telephone receiver in the secondary circuit of the
induction coil in the primary circuit of which is the transmitter, the secondary
circuit being so arranged that the induced current passes through vibrative
electrodes, as well as the helix of the receiving electro-magnet as herein described,
whereby the changes produced in the primary current by the vibrations of the
transmitting diaphragm are accompanied by simultaneous changes in the secondary
current produced by the corresponding vibrations of the receiving diaphragm.
The telephone transmitter consists of a diaphragm, a vibrating electrode, a
battery, the battery wires constituting the primary circuit of an induction coil,
a helix in snid primary circuit and a core, the secondary wires, a helix of the
induction coil wound upon the helix of the primary wire. One of the secondary
wires is grounded in the usual way, and the other wire extends to the receiver
and then to ground. This is the most simple form of an ordinary contact
transmitter.
The diaphragm of the receiver is mounted in a case or holder in the usual way,
and has secured to it a contact piece or electrode. On the core of the receiving
electro-magnet is wound a helix in the secondary circuit. The said core is hollow
and into one end is fitted a screw plug. An armature is connected to one end

page_text: of a spiral spring that is placed in the hollow of said core, the opposite end of the
spring resting against the plug. On the said armature is fixed a contact point or
electrode, and the armature is thus arranged to vibrate freely under the influence
of the said magnet in front of the pole or poles of the saine and between the
magnet and the diaphragm with the described electrodes pointing towards each
other. The spring is to be so adjusted, that said electrodes will be in contact.
The course of the secondary circuit is from the coil of the secondary wire that is
grounded by another wire, through the secondary wire, the coil of the receiving
electro-magnet, and by another wire to the core, plug, spring, armature, electrodes,
and diaphragm of the receiver, and by wire to ground. The last wire may if
preferred be connected immediately to the electrode on the diaphragm as when
a diaphragm is used formed of a non-conducting material.
The armature must of course be made of soft iron or equivalent metal capable
of magnetic induction. The electrodes may be of steel, which material I find
enables the receiver to reproduce most distinctly articulate sounds, spoken at the
transmitter. But steel is subject to the objection that it will corrode at the point
of contact between the electrodes. On this account platinum electrodes are
preferable to steel although the reproduction of articulate sounds with platinum
electrodes is not quite so perfect as with steel electrodes. By the use of electrodes
one or both of carbon in this connection, corrosion will be obviated, but I find that
the articulation when carbon is employed is less distinct than with either platinum
or steel,
1 find that by making the vibrating electrodes a part of the secondary circuit
so that the induced current passes through them as described the reproduction of
articulate speech at the receiver is improved.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Herbert John Allison in the Patent Office on the 5th May 1884.
HERBERT JOHN ALLISON, of the firm of Allison Brothers, Patent Agents,
of Southampton Buildings, London, "AN IMPROVEMENT IN THE RECEIVING
INSTRUMENT OF SPEAKING TELEPHONES a communication to me from abroad
"
by James Hart Robertson, of Brooklyn, New York, United States of America,
My invention relates to a telephone receiver in the secondary circuit of an
induction coil in the primary circuit of which is the transmitter, the secondary
circuit being so arranged that the induced current passes through vibrative.
electrodes, as well as the helix of the receiving electro-magnet as herein described,
whereby the changes produced in the primary current by the vibrations of the
transmitting diaphragm are accompanied by simultaneous changes in the secondary
current produced by the corresponding vibrations of the receiving diaphragm.
The lower portion of the figure in the drawing represents a telephone
transmitter consisting of the diaphragm A, the vibrating electrode B, the
battery C, the battery wires a, constituting the primary circuit of an induction
coil, the helix D, in said primary circuit and core D', the secondary wires b, b',
the helix E, of the induction coil, wound upon the helix D, of the primary wire.
The wire b', is grounded in the usual way, and the wire b, extends to the receiver
and then to ground (not shown). This is the most simple form of an ordinary
contact transmitter.
The upper part of the figure represents my receiver in which J, is the diaphragm
mounted in a case or holder (not shown) in the usual way and having secured
to it a contact piece or electrode e. G, is the core of an electro-magnet, on which
is wound the helix F, in the secondary circuit. The said core is hollow and into
one end is fitted a screw plug H. I, is an armature connected to one end of a
spiral spring c, that is placed in the hollow of said core G, the opposite end of the
spring resting against the plug H. On the said armature is fixed the contact
point or electrode d, and the armature is thus arranged to vibrate freely under the
influence of the said magnet in front of the pole or poles of the same and between
the magnet and the diaphragm with the described electrodes pointing towards each
other. The spring c, is to be so adjusted that said electrodes will be in contact.
The course of the secondary circuit is as shown from the coil E, of the secondary
wire b, that is grounded by the wire b¹, through wire b, coil F, wire b², core G,
plug H, spring c, armature I, electrodes d, an e, diaphragm J, and wire b³ to
ground. The wire b³, may if preferred be connected immediately to the electrode e,
on the diaphragm as when a diaphragın is used formed of a non-conducting
material.
The armature I, must of course be made of soft iron or equivalent metal capable
of magnetic induction. The electrodes d, and e, may be of steel which material
I find enables the receiver to reproduce most distinctly articulate sounds, spoken
at the transmitter. But steel is subject to the objection that it will corrode at the
point of contact between the electrodes. On this account platinum electrodes are
preferable to steel although the reproduction of articulate sounds with platinum
electrodes is not quite so perfect as with steel electrodes. By the use of electrodes
one or both of carbon in this connection, corrosion will be obviated, but I find that
the articulation when carbon is employed is less distinct than with either platinum
or steel.
I find that by making the vibrating electrodes d, and e, a part of the secondary
circuit so that the induced current passes through them as described the reproduction
of articulate speech at the receiver is improved.

page_text: What I claim as my invention and desire to secure by Letters Patent is :-
In a telephone receiver, an electro-magnet in the secondary circuit of an
induction coil, in the primary circuit of which is the transmitter, the diaphragm
provided with an electrode, a vibrative armature provided with an electrode and
interposed between the magnet and the diaphragm, with the electrodes in contact
and forming part of the secondary circuit, so that the secondary circuit will pass
through said electrodes, all constructed and combined as and for the purpose
described.
In witness whereof, I, the said Herbert John Allison, have hereunto set my
hand and seal, this fifth day of May, in the year of our Lord one thousand eight
hundred and eighty-four.