and Telephone Lines.
Year: 1884

page_text: and Telephone Lines.
I JOHN CLAYTON MEWBURN of 169 Fleet Street in the City of London Fellow
of the Institute of Patent Agents do hereby declare the nature of my invention for
IMPROVEMENTS IN MEANS OF SUPPRESSING INDUCTION IN TELEGRAPH AND
TELEPHONE LINES to be as follows:-
One of the main obstacles which have hitherto prevented the use of telephonic
transmissions from becoming more general is the induction due to neighboring
wires upon the wire used for transmitting speech. When the lines are more than,
say, a hundred metres long, this induction even renders telephonic transmission
impossible.
The object of this invention is to suppress this induction and this object is
attained by means of devices hereinafter described. These devices are based upon
the following principle :-
Suppose, for instance, two telegraphic lines A C, A¹ C to be arranged very close
to each other, the one for transmitting ordinary telegraphic messages, and the other
connected to a telephone. If now an electric current of a rapidly varying intensity
be sent through the line AC (this taking place during the period termed the
variable state, during which the current passes through all the degrees included
between zero and its definite intensity, which latter degree it generally reaches in
a very short time) the line A¹ C¹ will then become the seat of production of electro
motive forces of induction which will be proportionate to the length of the two
lines and will depend upon their distance.
These electro motive forces will then generate in A¹ C¹ a current of short
duration but which will strongly affect the telephone, so that if the induced
currents follow each other rapidly they will cause in the instrument a series of
violent and closely succeeding shocks, which render the use of the telephone
impracticable.
Now according to this invention there is generated or engendered at any point
whatsoever of the telephone liue A¹ C₁ electro motive forces every instant and of
contrary polarity equal to those developed throughout the whole length of this line
by the line A C. To accomplish this result, there is placed at any suitable point of
CD
A

page_text: 68
the line AC, a coil B containing in a small volume a considerable quantity
of spirally wound copper wire and having consequently a low resistance and a high
inductive power. Next to this coil and at a distance determined by conditions
which are hereinafter set forth, there is placed another coil B which may be either
similar to, or different from the former, and is connected with the line A¹ C¹.
These two coils I will term compensating coils." Now if a current of a rapidly
varying intensity, as above stated, be sent through the line A C, the coil B will
produce, by induction, in the coil B¹, an electro motive force always proportionate
to that produced by the whole line A C upon the line A¹ C₁ because all the
variations which the current undergoes in the line AC are accurately reproduced
in the coil B. The coil B¹ will therefore through the whole period of induction be
absolutely like a battery, both the poles of which would be at disposition, and
the electro motive forces of which would depend upon the length of the wound
wire, and upon the relative position of the two coils B and B¹. One can
consequently and at pleasure add the electro motive forces due to induction of the
line AC upon the line A¹ C₁ to those resulting from the action of B upon B¹, or
else one could deduct the same according to whether the line A¹ C¹ be connected
with the one or the other end of the coil B¹. In the first case, the intensity of the
current induced by the line A C on A¹ C¹ would increase; in the second, it would
decrease. The extent of such increase or decrease would as before stated depend
upon the number of the spirals of the two coils and their relative position. Now
it is easy to impart to that number of spirals a sufficient value so that, the two
coils being exactly superposed, the electro motive forces of induction developed
by B upon B' shall be of contrary polarity to, and much greater than that which
is due to the action of A. C upon A¹ C¹. Therefore if it be desired that the two
electro motive forces should become exactly equal to each other while being of
contrary polarity, it will be sufficient to displace the coils with relation to each
other until the telephone in the line A¹ C¹ remains silent in spite of the passage of
intermittent alternate or undulatory currents through the line A C.
In order that this may be better understood it may be stated that the two
lines AC and A¹ C' induce each other reciprocally as would be the case with two
coils similar to the coils B and B¹ and that these latter cause to be counterbalanced
the inductive forces generated in the ideal coils replacing AC and A¹ C¹ which is
a condition easy to fulfil by suitably connecting them. It will be easily under-
stood that if there be in the same room four coils of which two would induce the
other two in pairs, they could always be grouped so as to destroy the induction of
the first pair of coils upon the second pair. It will be well to notice that if by the
use of the compensating coils, things are so arranged that the line AC is no longer
capable of developing induced currents in the line A'C', this line A¹ C¹ in its turn
is no longer capable of developing induced currents in the line A C. These two
lines consequently act exactly as though they were very far apart and therefore in-
each of these lines, there can be simultaneously or successively sent currents of any
kind whatsoever whether intermittent, alternate or undulatory, such for instance,
as are generally used in the various telegraphic or telephonic systems without the
said lines being in any way influenced by each other. The system is accordingly
further applicable to a group or set composed of telephonic lines only.
If it be desired to attain the same end in cases where there are more than two
wires, the induction of each wire on every other wire must be balanced in the same
way, that is to say if there were for instance, four wires it would be necessary to
balance the induction of wire No 1 on wire No 2.
of wire No 1 on wire N° 3.
of wire No 1 on wire No 4.

page_text: placed on the wires at the telegraph poles. This condition is not however
indispensable although it may be of advantage in some cases. The compensating
coils may in fact, be placed either at the trausmitting station, or at the receiving
station, but, in such cases, care should be taken that the pairs of coils intended to
balance the induction of the lines should be so arranged, two and two, as to prevent
any one pair from influencing or being influenced by any other. Thus for instance,
the pair of coils which destroy the mutual induction of the lines 1 and 2 should
not be influenced by any one of the pairs of coils used for compensating the
inductions of the lines N° 1 and 3, 1 and 4 and so forth. This result may be
obtained in different ways for instance by enclosing each pair of coils in a metal
casing having sufficiently thick walls.
-
Generally speaking in order to destroy induction on a group of say n wires, it is
necessary that on each one of these wires there be n 1 coils so that the total
number of coils will be equal to n (n - 1).
These compensating coils may either be flat coils of equal sizes and capable of
being brought in contact or they may be concentric solenoids capable of being
entirely inserted into each other.
It is evident that if a core of wires be inserted in the coils, the efficiency of these
coils will increase, that is to say, they could then produce the same effect with a less
amount of copper wire.
It has already been mentioned that the electro-motive force of induction developed
by the coil B upon the coil B¹ is at all times proportionate to that resulting from
the action of the line A C upon the line A' C₁ but that with regard to its absolute
value it depends upon the length of the wire wound upon such coils, as well as
upon their relative position. Now the object is to give this electro motive force a
value exactly equal to that produced by the line AC upon the line A¹ C¹, and to
accomplish this, suitable controlling or regulating means or devices must be
provided; I will proceed to describe several devices adapted for this purpose.
In one of these devices the coils are simply tightly wound spirals B and B¹ the
insulating material of each being removed only on one of their plane faces. If the
line A C be connected to one of the ends of the spiral B and an extension of the
line be attached to a friction spring capable of being moved away from or towards
the centre of the spiral, it is evident that it will be sufficient to cause the said
friction spring to slide so that the number of sections of the spiral engaged in the
line can be more or less as the case may be, so that the inductive action produce l
by this coil upon spiral B' may be as much reduced as desired. This secon.!
spiral B is arranged exactly as the spiral B as regards the connections with its line
and a friction spring. In order to augment still further the precision of these
means of regulation the number of spiral sections through which the current passes
may be increased or decreased by a fraction of a turn only, by imparting any
desired limited extent of rotation to the spirals by means of a button.
Another means of regulating consists in causing one of the two coils to slide
flatwise upon the other. In this case the most energetic action takes place when
the two centres coincide.
In another mode of regulation one of the coils B is stationary and the other E¹
movable around an axis. The latter coil is sinaller than the coil B so that it may,
if necessary, be placed concentrically to B and in the same plane. By causing the
coil B¹ to turn by means of a button from the position it occupies in the same plane
with B, to that where it becomes perpendicular or at right angles to B, the
inductive action of B upon B¹ can be made to vary from maximum to zero.
In another device the desired regulation is obtained by causing B¹ to move a
greater or less distance away from B, the two coils being always parallel.
To effect this it will suffice to turn a button; a rod attached to B¹ and threaded is
screwed into or unscrewed from the support of the stationary coil B and thus the
requisite distance apart of the two coils can be obtained with the greatest accuracy.
In this arrangement however, the action of one of the two coils upon the other
could not possibly be brought to zero, but if this were desired it will suffice to

page_text: divide the coil B into two stationary parts or coils while B¹ is movable between
them. The connections of the line with these two coils are such as to produce
on B¹ actions of contrary polarity which vigorously counterbalance or annul each
other when B¹ is exactly in the middle of the interval between the two stationary
coils. If by means of a button the movable coil B¹ be placed somewhat closer to
one of the stationary coils than to the other, the action of the first will prevail and
this all the more as the difference in distance is greater.
In another device for regulating, the stationary coil B is also divided into two
parts which assume a semi circular shape and are set on a stationary disc. The
movable coil is similarly divided and its two semi-circular halves are fixed on a
spindle terminated by a button.
Now when the four half circumferences composing the two coils coincide, the
inductive action produced by the stationary upon the movable coils reaches its
maximum; when on the contrary the diameter of the movable coils is at right
angles to the diameter of the stationary coils this action is null.
It will be observed that the use of induction coils, as herein described, does not
in any way modify either the construction of telegraphic or telephonic instruments
or the method of operating the same, the results obtained by means of the com-
pensating coils are independent of the intensity of the currents sent through the
lines or of the electrical resistance of such lines. If, therefore the regulation is
properly effected by suitably placing the coils and by means of any of the herein-
before described devices, the regulation will remain permanent whatever may be
the variations of the currents sent through each line and the temperature of the
atmosphere.

page_text: Improvements in Means of Suppressing Induction in Telegraph
and Telephone Lines.
I JOHN CLAYTON MEWBURN, of 169 Fleet Street in the City of London, Fellow
of the Institute of Patent Agents do hereby declare the nature of my invention for
IN
"
MEANS
OF SUPPRESSING INDUCTION
IN TELEGRAPH
AND
"IMPROVEMENTS
TELEPHONE LINES and in what manner the same is to be performed, to bo
particularly described and ascertained in and by the following statement:-
One of the main obstacles which have hitherto prevented the use of telephonic
transmissions from becoming more general is the induction due to neighboring
wires upon the wire used for transmitting speech. When the lines are more than,
say, a hundred metres long, this induction even renders telephonic transmission
impossible.
The object of this invention is to suppress this induction and this object is
attained by means of devices hereinafter described. These devices are based upon
the following principle:-
Suppose, for instance, two telegraphic lines A. C, A', C¹ (Figure 1) to be arranged
very close to each other, the one for transmitting ordinary telegraphic messages,
and the other connected to a telephone. If, now, an electric current of a rapidly
varying intensity be sent through the line A, C (this taking place during the
period termed the variable state, during which the current passes through all the
degrees included between zero and its definite intensity, which latter degree it
generally reaches in a very short time) the line A¹ C¹ will then become the seat of
production of electro-motive forces of induction which will be proportionate to the
length of the two lines, and will depend upon their distance.
These electromotive forces will then generate, in A¹ C¹, a current of short
duration, but which will strongly affect the telephone, so that if the induced
currents follow each other rapidly, they will cause in the instrument a series of
violent and closely succeeding shocks, which render the use of the telephone
impracticable.
Now according to the present invention there is generated or engendered, at
any point whatsoever of the telephone line A¹, C₁ electro-motive forces every
instant and of contrary polarity equal to those developed throughout the whole
length of this line, by the line A C. To accomplish this result, there is placed at
any suitable point of the line A, C, a coil B containing in a small volume a con-
siderable quantity of spirally wound copper wire, and having consequently a
low resistance and a high inductive power. Next to this coil and at a distance
determined by conditions which are hereinafter set forth, there is placed another
coil B¹ which may be either similar to,, or different from the former, and is
connected with the line A¹ C. These two coils I will term "compensating coils."
Now, if a current of a rapidly varying intensity, as above stated, be sent through
the line A C, the coil B will produce, by induction, in the coil B¹, an electro-motive
force always proportionate to that produced by the whole line A, C upon the
line A C¹, because all the variations which the current undergoes in the line A C,

page_text: are accurately reproduced in the coil B. The coil B¹ will therefore, through the
whole period of induction be absolutely like a battery, both the poles of which
would be at disposition and the electro-motive forces of which would depend upon
the length of the wound wire, and upon the relative position of the two coils B
and B¹. One can consequently and at pleasure add the electro-motive forces, due
to induction of the line A, C upon the line A¹ C¹, to those resulting from the action
of B upon B¹, or else one could deduct the same according to whether the line A¹ C¹
be connected with the one or the other end of the coil B. In the first case, the
intensity of the current induced by the line A, C on A³ C¹ would increase; in the
second, it would decrease. The extent of such increase or decrease would, as
before stated, depend upon the number of the spirals of the two coils and their
relative position. Now, it is easy to impart to that number of spirals a sufficient
value so that, the two coils being exactly superposed, the electro-motive forces of
induction developed by B upon B shall be of contrary polarity to, and much
greater than, that which is due to the action of A, C upon A¹ C. Therefore if it
be desired that the two electro-motive forces should become exactly equal to each
other while being of contrary polarity, it will be sufficient to displace the coils
with relation to each other until the telephone in the line A¹ C¹ remains silent, in
spite of the passage of intermittent, alternate or undulatory currents through the
line A C.
-
In order that this may be better understood it may be stated, that the two
lines A. C and A¹ C¹ induce each other reciprocally as would be the case with two
coils similar to the coils B and B¹, and that these latter cause to be counterbalanced
the inductive forces generated in the ideal coils replacing A C and A¹ C', which is
a condition easy to fulfil by suitably connecting them. It will be easily understood
that if there be in the same room four coils of which two would induce the other
two in pairs, they could always be grouped so as to destroy the induction of the
first pair of coils upon the second pair. It will be well to notice that if by the
use of the compensating coils, things are so arranged, that the line A. C is no longer
capable of developing induced currents in the line A¹ C¹, this line A C¹, in its
turn, is no longer capable of developing induced currents in the line A, C. These
two lines consequently act exactly as though they were very far apart and therefore
in each of these lines there can be simultaneously or successively sent currents of
any kind whatsoever, whether intermittent, alternate or undulatory, such, for
instance, as are generally used in the various telegraphic or telephonic systems,
without the said lines being in any way influenced by each other. The system
is accordingly further applicable to a group or set composed of telephonic lines
only.
If it be desired to attain the same end in cases where there are more than two
wires, the induction of each wire on every other wire must be balanced in the same
way, that is to say if there were, for instance, four wires, it would be necessary to
balance the induction of wire N° 1 on wire N° 2.
of wire N° 1 on wire N° 3.
of wire N° 1 on wire N° 4.
of wire N° 2 on wire N° 3.
of wire No 2 on wire N° 4.
of wire N° 3 on wire N° 4.
This result will be accomplished if each wire be provided with three coils
arranged as shown in the diagram Figure 2, wherein the coils are supposed to be
distributed along the line itself, as would, for instance, be the case if they were placed
on the wires at the telegraph poles. This condition is not, however, indispensable
although it may be of advantage in some cases. The compensating coils may, in
fact, be placed, either at the transmitting station, or at the receiving station; but,
in such cases, care should be taken that the pairs of coils, intended to balance the
induction of the lines should be so arranged, two and two, as to prevent any one
pair from influencing or being influenced by any other. Thus, for instance, the
pair of coils, which destroy the mutual induction of the lines 1 and 2 should not

page_text: be influenced by any one of the pairs of coils used for compensating the inductions
of the lines N° 1 and 3, 1 and 4 and so forth. This result may be obtained in
different ways for instance by enclosing each pair of coils in a metal casing having
sufficiently thick walls.
Generally speaking in order to destroy induction on a group of, say, n wires, it
is necessary that on each one of these wires there be n-1 coils so that the total
number of coils will be equal to n (n-1).
These compensating coils may either be flat coils of equal sizes and capable of
being brought in contact; as shown in Figure 1, or they may be concentric
solenoids B B¹, capable of being entirely inserted into each other, as shown in
Figure 3, in which the smaller solenoid B is only partially introduced into the
larger B¹.
It is evident that if a core of wires be inserted in the coils, the efficiency of
these coils will increase, that is to say they could then produce the same effect with
a less amount of copper wire.
It has already been mentioned that the electro-motive force of induction
developed by the coil B upon the coil B¹, is at all times proportionate to that
resulting from the action of the line A, C upon the line A¹ C¹, but, that, with
regard to its absolute value, it depends upon the length of the wire wound upon
such coils, as well as upon their relative position. Now, the object is to give this
electro-motive force a value exactly equal to that produced by the line AC upon
the line A¹ C'; and to accomplish this, suitable controlling or regulating means or
devices must be provided; I will proceed to describe several devices adapted for
this purpose; they are represented in Figures 4 to 8.
In Figure 4, the coils are simply tightly wound spirals B and B₁ the insulating
material of each being removed only on one of their plane faces. If the line A Č
be connected to one of the ends A of the spiral B, and an extension D of the line
be attached to a friction spring f, capable of being moved away from or towards
the centre of the spiral, it is evident that it will be sufficient to cause the said
friction spring to slide so that the number of sections of the spiral engaged in the
line can be more or less as the case may be, so that the inductive action produced
by this coil upon spiral B₁ may be as much reduced as desired. This second
spiral B' is arranged exactly as the spiral B, as regards the connections with the
line CA¹ D' and the friction spring f. In order to augment still further
the precision of these means of regulation the number of spiral sections through
which the current passes may be increased or decreased by a fraction of a turn
only, by imparting any desired limited extent of rotation to the spirals B B' by
means of a button M.
Another means of regulating shown in Figure 5 consists in causing one of the
two coils B and B¹ to slide flatwise upon the other. In this case the most energetic
action takes place when the two centres coincide, as is the case in the first of the
two positions shown in the Figure.
In another mode of regulation, shewn in Figure 6 one of the coils, B, is stationary,
and the other, B¹, moveable around an axis. The latter coil is sinaller than the
coil B so that it may, if necessary, be placed concentrically to B and in the same
plane. By causing the coil B' to turn by means of the button M, from the position
it occupies in the same plane with B, to that where it becomes perpendicular or at
right angles to B, the inductive action of B upon B¹ can be made to vary from
maximum to zero.
In another device, shown in Figure 7, the desired regulation is obtained by
causing B' to move a greater or less distance away from B, the two coils being
always parallel. To effect this, it will suffice to turn the button; the rod that is
attached to B', being threaded, is screwed into or unscrewed from the support b of
the stationary coil B, and thus the requisite distance apart of the two coils can
be obtained with the greatest accuracy.
In this arrangement, however, the action of one of the two coils upon the other
could not possibly be brought to zero; but, if this were desired, it will suffice to

page_text: divide the coil B, B into 2 stationary parts or coils, as shown in Figure 8, while B'
is moveable between them. The connections of the line D, C (Figure 1) with
these two coils are such as to produce on B¹ actions of contrary polarity, which
vigorously counterbalance or annul each other, when B₁ is exactly in the middle of
the interval between the two stationary coils B B. If, by means of the button M,
the movable coil B¹ be placed somewhat closer to one of the stationary coils B, B
than to the other, the action of the first will prevail, and this all the more as the
difference in distance is greater.
In another device for regulating; shown in Figure 9 the stationary coil B is
also divided into two parts B and B₁ which assume a semi-circular shape and are
set on a stationary disc P. The movable coil is similarly divided into two
parts B¹ and B¹, and its two semi-circular halves are fixed on a spindle a terminated
by a button M.
Now when the four half-circumferences composing the two coils coincide, the
inductive action produced by the stationary coils B B, upon the movable coils B' B₁₁
reaches its maximum; when on the contrary the diameter of the movable coils B¹ B¹
is at right angles to the diameter of the stationary coils B, B₁ this action is null.
It will be observed that the use of induction coils, as herein described, does not
in any way modify either the construction of telegraphic or telephonic instruments
or the method of operating the same; the results obtained by means of the
compensating coils are independent of the intensity of the currents sent through
the lines or of the electrical resistance of such lines. If, therefore, the regulation
is properly effected; by suitably placing the coils and by means of any of the
herein before described devices, the regulation will remain permanent whatever may
be the variations of the currents sent through each line and the temperature of the
atmosphere.
Having now particularly described and ascertained the nature of my said
Invention, and in what manner the same is to be performed, as communicated to
I declare that what I claim is
me,
First. The use, for the purpose of counteracting and destroying or suppressing
telegraphic and telephonic induction in closely arranged wires belonging to the
same group, of coils substantially as described acting upon each other by induction,
and connected to each of the wires substantially as described, so as to generate, at
any one or more points of the circuit, electro-motive forces remaining at all times
equal, but of contrary polarity, to those electro-motive forces which are due to
the mutual induction of the wires, as set forth.
Secondly. The various arrangements for regulating the relative positions of the
compensating coils, substantially as described and shown in the accompanying
drawings.