IMPROVEMENTS IN ARRANGEMENTS OF TELEPHONIC APPARATUS
Year: 1884

page_text: I SILVANUS PHILLIPS THOMPSON of University College, Bristol, in the City and
County of Bristol, Doctor of Science and Professor of Experimental Physics do
hereby declare the nature of my invention, for IMPROVEMENTS IN ARRANGEMENTS
OF TELEPHONIC APPARATUS to be as follows:-
This invention relates to improvements in the arrangement of Telephonic
apparatus of the type described in the English Mechanic of August the 11th 1876,
in which the armatures are carried on a membrane and my improvements are
intended to render the same more efficient in action and better adapted for working
both as transmitting and as receiving apparatus when working in direct circuit,
and as receiving apparatus when working in an induction-circuit. I employ a
membrane carrying at its centre an armature of thin iron or steel. The armature
so mounted on its membrane I place in front of the pole or poles of an electro-
magnet, and I excite this electromagnet by a current which I throw into the line
wire or main circuit by means of a battery inserted in the main line so that the
telephonic currents coming from the line or main circuit must pass first through
the battery before they reach the receiver. I connect a shunt circuit from the line
at a point in the line anterior to the line battery, to a point posterior to the
receiving telephone, and insert in this loop-circuit an electromagnet of considerable
self-induction in order that the latter may by its great electric inertia plug the
shunt-circuit with respect to the rapidly-fluctuating telephonic currents and force
them to traverse by the main line through the battery in the line wire and through
the receiver which is in the main line. In some cases I simply carry a shunt
line from a point on the main line anterior to the line-battery, and connect it
through an electromagnet of great electric inertia to the earth.
Dated this 10th dox of June 1901.

page_text: "
I, SILVANUS PHILLIPS THOMPSON of University College, Bristol, Doctor of
Science and Professor of Experimental Physics do hereby declare the nature of my
invention for "IMPROVEMENTS IN ARRANGEMENTS OF TELEPHONIC APPARATUS
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 Telephonic Apparatus and is designed to increase the
efficiency of instruments of the class or type described in the "English Mechanic
and World of Science" of August 11th 1876.
My said Invention comprises the combination of an instrument of this class
hereinafter referred to as an electro magnetic telephone instrument with means for
rendering the said instrument more efficient than heretofore both in transmitting
and receiving when working in an induction circuit.
My Invention is illustrated in the, accompanying drawing which shews diagrams
of alternate arrangements of circuits and apparatus.
In electro magnetic telephone instruments that is to say, instruments wherein
there is an electro magnet excited by a battery in the main circuit or line wire as
'described in the publication above referred to, the difficulty found hitherto in
working in induction circuits arises from the lack of sensitiveness of the Instru-
ment, and this in turn is chiefly due to the high resistance of the wire ordinarily
used on the line, the effect whereof is to diminish the initial current in the receiver
coil, which current should be sufficient to magnetize the core of the electro magnet
somewhat strongly. To obviate this difficulty and attain the requisite sensitiveness
of the Instrument without being obliged to use an inordinate number of cells,
I connect with the line wire a loop or shunt circuit as shewn in Figure 1 of the
accompanying drawings extending from a point P in the line anterior to the line
battery Z. Y through an electro magnet to a point Q posterior to the receiving
Telephone R.
し
If this shunt circuit were merely a shunt with a resistance of more or less value
or amount it would not satisfactorily serve the purpose of my Invention for
although it would by reason of its greater or less resistance allow a considerable
part of the battery current to run through it thereby causing an increased current
through the receiver and ensuring an adequate magnetization of the core of its
electro magnet yet it would not fully serve my purpose because the " working
currents
"
or voice currents coming through the main line would be partially
diverted into the shunt and would without passing through the receiver leak
through the said shunt to earth-This method of working that is to say by
shunting or diverting a portion of the current from the receiver is altogether
distinct and different from and would prevent the attainment of the object
of my Invention which is based upon the principle of blocking the loop or
shunt circuit against the fluctuating voice currents or telephonic currents coming
along the main line while allowing the flow of the steady battery current through
the said loop,

page_text: For
purpose it is necessary to interpose in the loop or shunt circuit, a
device or organ which while having very little resistance possesses great electric
inertia or in other words has a high co-efficient of self induction.
I therefore insert in this loop circuit an electro magnet S constructed with a
large number of turns of wire surrounding an iron core to ensure the required
co-efficient of self induction in order that by its great electric inertia it will block
or "plug" the loop or shunt circuit with respect to the rapidly fluctuating
telephonic currents and ensure their traversing the main line, the battery in the
main line and the receiver which is also in the main line.
.The electro magnet in the shunt circuit which for the purpose of my Invention
must in all cases have a high co-efficient of self induction relatively to its electrical
resistance I call an "induction plug" because of the well known property of such
an electro magnet of obstructing by its great electro magnetic inertia, the passage
of rapidly fluctuating currents, an electro magnet so constructed and arranged will
prevent the rapidly fluctuating currents from being diverted through the shunt
circuit to earth and will force them almost entirely to traverse the main line through
the receiving Telephone.
I have herein above stated that this plugged loop line is not a mere shunt
through which the voice currents would leak away, furthermore, I wish it under-
stood that my Invention is distinct from any system of simultaneous Telegraphy
and Telephony in which an electro magnet or coil is used for the purpose of
separating the Telephonic from the telegraphic currents, for my purpose the
resistance should be as small as possible and it would best answer my purpose to
have if practicable an electro magnet without any resistance. The wires that
connect the electro magnet with the main circuit should also have an inappreciably
small resistance.
In some instances I adopt the arrangement shewn in Figure 2 that is to say
I extend a loop line or shunt circuit from a point P on the main line anterior to
the line battery and connect it through an electro magnet or induction plug S of
great electric inertia to the earth at E.
In figure 3 I have illustrated an arrangement of the circuit to be adopted when
this Invention is used in connection with the valve Telephones described in the
Specification of Letters Patent applied for by myself and "P. Jolin N° 8524 A.D.
1884.
By my Invention I increase the efficiency and sensitiveness of instruments of
the above specified class or type namely those excited by a Battery which is in the
main circuit or line wire and moreover instruments of this type are rendered more
efficient for transmitting as well as for receiving by my method of applying a loop
line blocked or plugged against the Telephonic currents by the insertion of an
electro magnetic induction plug.
In the Drawing which I have herein above partly described figure 1 shews a
portion of the main line wire at L. L. with the battery Z. Y. included therein, the
loop or shunt circuit is shewn extending from the point P anterior to the battery
to the point Q posterior to the Receiver R which is between the point Q and the
battery. S is the electromagnet or induction plug in the said loop or shunt circuit.
The end of the main line below or posterior to the point Q is connected to earth
as shewn at E or to a return wire.
The arrangement shewn in figure 2 differs from that in figure I only in respect
of the direction of the loop or shunt circuit which extends from the point P to
earth as above specified.
In figure 3 the main circuit or line wire L the position of the battery Z Y and
the connection of the loop or shunt circuit with the point P are the same as in
figures 1 and 2. C is an induction coil T is the transmitter. The line circuit is
through the battery Z. Y. the receiver R and the secondary wire c c¹ of the said
induction coil to earth, the transmitter circuit starts from the battery Z. Y (part of
which is utilized for the primary circuit) and divides preferably into two branches,

page_text: one branch extends through p, p' and through the transmitter T, the other branch
extends through p, p and through a compensating resistance W. These two
branches which form a double primary; of the induction coil C re-unite at A, whence
the circuit returns to the battery.
:
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
I claim is
re
The herein before, described combination of an electro magnetic telephone instru-
ment with an induction plug, which permits a steady battery current to flow
through the electro magnet of the telephone instruments by means of a shunt
circuit, but prevents the fluctuating voice currents from passing round the shunt
circuit and causes them to pass through the telephone instrument.
Dated this 19th day of March 1885
SILVANUS PHILLIPS THOMPSON.