Improvements in the Method of and Means for Preventing Undue between Reciprocal Influences between Telephonic Lines, or Telephonic and Telegraphic or other Electrical Lines.
Year: 1894

page_text: Date of Application, 9th Aug., 1894-Accepted, 9th Aug., 1895
COMPLETE SPECIFICATION.
Improvements in the Method of and Means for Preventing Undue
between
Reciprocal Influences between Telephonic Lines, or
Telephonic and Telegraphic or other Electrical Lines.
I, EMIL MÜLLER of No. 31 Rykestrasse, Berlin in the Kingdom of Prussia, in
the Empire of Germany, Telegraph Engineer, 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 improvements in the method of and means for preventing
the undue reciprocal influences between two or more telephone lines, as also between
telephonic and telegraphic or other electrical lines and by the said method and
means I subdue the noise in telephones usually termed "cross talking," which, as is
generally known, forms a great obstacle to a clear understanding of telephonical
communications.
Where two or more telephonic lines, whether single or double, are running parallel
to each other to some extent, a reciprocal influence of these lines is experienced in
such a manner, that communications carried on by one line are more or less distinctly
heard through the neighbouring lines. The so-called "cross talking" thereby
occasioned, is most inconvenient, but the undue influences on the telephonic line are
still more aggravating, where neighbouring lines are used for telegraphic service or
even for conveying electrical energy.
Up to this time the origin of such undue reciprocal influence between electrical
lines has been attributed to electro-static induction, and accordingly, the means
hitherto proposed and tried to prevent or mitigate such undue influences, have all
been based on such supposition. The lines for the telegraphic service and those for
distributing electrical energy have, as a principle, been carried along poles or
supports as far as possible distanced from those of the telephonic conductors, while,
to counteract the reciprocal influence between two or more telephonical lines,
recourse is usually had to crossing the wires.
Said crossing consists in changing the reciprocal position of the conductors at as
many portions of the line as may be practically realized, for instance, at every fourth
pole by said crossings the sum of all the individual actions of the portions of length
is calculated to be nought.
But all these means hitherto practised for preventing the undue influences are
connected with serious inconveniences and difficulties for the telephonic service.
The use of separate and independent poles or supports for the telephone wire-
lines increases the expense and in many cases great difficulties must be overcome in
order to find and obtain suitable tracks for establishing the poles or supports. And,
further, the crossings of the telephonic lines not only materially add to the expense
of establishing the line, but also of maintaining the same, and, in spite of all this
the means employed fail to give a satisfactory result, particularly in a moist
atmosphere.
My invention is founded on the observation, that the cause of the undue influences
referred to is falsely attributed to the effects of induction, the reciprocal influence
of telephonic lines between each other and between other electrical lines must be
explained as originating from a direct passage of the current from one line to the
other, even in those cases where the lines are carried by separate but neighbouring
sunnoris

page_text: results are obtained :-
metrou aou means neremarter described, the fon
First Any convenient number of telephonic forward and return conducting
lines may be carried by the same poles without having to cross the wires;
Second Telegraphic lines and telephonic forward and return conducting lines
may be carried by common poles ;
Third: In telephonic single lines of considerable extent the so called cross-talk
is reduced to such an extent as to lose its undue effect in the service;
Fourth: The undue effect of neighbouring lines for conducting electrical energy
ou telephonic lines is subdued.
Admitting my said observation to be correct, it might be observed that the best
means for preventing the undue influences in question would consist in establishing
an absolute insulation, whereby all passage of current from one line to the other
would be stopped. But no insulating means are known which entirely prevent the
escape of the current. Accordingly, my invention provides means of a different
kind, and the insulators hitherto employed may, henceforth, be used as before.
The characteristic feature of my invention consists in, first, reducing to a
minimum the escape of current from a forward and return conductor, and its passage
into neighbouring lines, and, second, in counteracting the effect of currents actually
escaping into such neighbouring lines by means of a special system of distribution.
My invention will be more fully understood if explained with reference to the
accompanying drawings.
In Figure 1, P is an ordinary pole of wood carrying the two supports A and A
for the forward and return conductor of a telephonic line; B and B' are the two
supports of another telephonic line carried by the same pole P.
Owing to the fact that no insulation is absolutely perfect, small parts of the
current flowing through the circuit A A¹ will escape at the support A and pass
through the said support on to the wood pole P through which they will be
distributed to the supports A¹ B and B and down to the ground. This distribution
is of a very complicated nature, but at any rate parts of the current pass from the
circuit A A into the circuit B B and there cause the so-called cross-talk.
The natural tendency of the electrical tension existing in the circuit A A¹ is that
of immediately reciprocally uniting, but this, however, is prevented by the
insulators, and, owing to this circumstance, the current is forced to proceed through
the entire length of the circuit. Those portions of the current which escape at the
insulators and pass into the supports A A' have the same tendency to unite on the
shortest possible way, but as the wood of the pole l' is an obstacle to their uniting
immediately, they take any way that offers itself for meeting, and, in being
distributed, pass into the supports B B₁ of the other line. To prevent this, I first
arrange means to facilitate the immediate meeting of those portions of the current
which unavoidably used to escape at the insulators A A¹ thereby preventing them
being distributed over the pole P, and I further provide means to prevent such
swerving portions of the current from entering into the line carried by the
supports B B, by such means the latter line will no more be influenced by the
line A A¹.
To allow the escaping portions of the current to meet immediately, I connect
the supports A and A which may consist of iron, as in Figure 3, or of wood or
other material, by a metallic conductor N, and by the direct passage of said portion
of the current from A to A', distribution over the pole P is prevented, the current
preferring the shortest way.
The connection N, as shown in Figure 3, serves to realise the object of my
invention in existing lines where the supports A and A' are placed distant from
each other; but in establishing new lines, an arrangement of still greater
simplicity may be preferred which is represented in Figure 34, and consists in
placing the two supports A A', of a circuit on a common rod or bar N₁ of
conducting metal thereby enabling the portions of current, which escape at A, to

page_text: mmediately pass over and into the support A¹ for uniting with the other branch of
he circuit without being distributed over the pole P.
The system shown in Figure 3 is further improved, if in addition to such direct
connection of the supports, the insulation of the said supports is made more
complete.
An insulating device of this kind which is illustrated by Figure 2 consists of
auxiliary insulating supports a a' fixed to the pole P and carrying a metal rod S to
which the line carrying insulators A A' are fixed. The insulating supports BB¹
of the other line are carried by a similar metal rod T, carried by auxiliary
insulating supports bb. The portions of current escaping at A pass immediately
through the rod S to A', and, meeting with the portions escaping at A', are
neutralised. But if the difference of tension in the current at A and A¹ is
considerable, such difference of current cannot reach the supporting rod T before
first overcoming the obstacle of the insulators at a a', then that of the pole P and,
finally, that of the insulators at b b¹. ·.
This improved insulating device, however, will not be necessary in all cases, its
use being principally destined for such cases where telephonic forward and return
lines are carried by the same poles with telegraphic lines of the Morse- or Hughes-
system, or with electrical lines for conveying electrical energy. For general use,
the arrangement of a connecting conductor N or N', as shown in Figures 3 and 3^.
between the insulating supports of a telephonic circuit will he found sufficient.
The reciprocal position of the two branches of the circuit is of no avail, and the
satisfactory results of my invention are not the least impaired by any difference in
the shape or arrangement of the supports carrying the insulators or in the shape
and position of the metallic conductor which connects the said supports.
As long as the portions of current escaping at the insulators A and A' are equal
to each other, they will be neutralised by meeting, as described, but when the
positive, or the negative electricity of the escaping currents prevails, the difference
of such currents will pass on to the next following insulators, and, owing to the
metallic connection between the two supports belonging to the line, it will pass
into the conductors of the telephonic circuit. This overflow of current following
the law of the distribution of currents under ordinary circumstances will influence
the receiver in the second circuit.
To prevent this, I provide means, by which I obtain that the amount of current
escaping from the line, whether single or double, may pass into both branches of
the neighbouring double line in such a manner, that an equal portion of said current
enters into each of said branches. The effect will be, that, from the point where
the escaping current enters into the double line, equal amounts of electricity of the
same polarity will flow to the ends of the circuit and there neutralize each other
by forming an indifferent point. The telephonic receiver, being located at such
indifferent point, will not be influenced by the current, which has unduly entered
into the circuit.
In practice, the said indifferent point will be coincident with that point, where
the undulations of the current are generated, i.e., with a telephonic double line, it
will rest in the secondary wire of the induction coil for the microphone. Where a
single line is combined with a double line, the indifferent point should be located in
one of the wires of the coil which transmits the induction.
Referring to Figure 4 in which i represents the induction coils, CD, and C¹ D¹
the line wires and N the hereinbetore described metallic connections between
the supports of the line wires, if from a neighbouring iine amounts of escaping
current should pass into the double line C, D, C, D, indifferent points will be
formed in the top- or angle points C, C, and D, D₁ of said circuit. To obtain
this, the resistance in the branch C, D, must be equal to that in the branch C¹, D¹.
A uniform resistance in the two branches is obtained by measuring the amount
5 of resistance existing in each of them, and by connecting auxiliary resistances
at the ends of the branches, each of which auxiliary resistances makes up

page_text: one half of the difference between the two branches to balance the same.. The
connection of the waker-apparatus (relay, alarm) accordingly, must not be made on
one side, but in the form of a bridge d, as shown in Figure 5, i being the induction
coils and CD, and C₁ D₁, the line wires and the receivers, all of a uniform
resistance, should be arranged at both sides of the source of current (the microphone
coil) as shown in Figure 6 whereby the total amount of resistance in the line
from E to F, Figure 6, will be equal to that in the branch from E¹ to F¹.
In telephonic single lines of long extent, the cross-talk caused by mutual
influence will never be entirely eliminated, but by providing suitable means, which
form another feature of my invention, such reciprocal influences may be reduced to
a minimum.
In telephonic lines of this kind, it has been tried to overcome the inconvenience
of cross-talking by connecting the insulator-supports of each pole to ground. But
this trial did not succeed for this reason, that the resistance of the separate
connections to ground at the poles could not he made sufficiently small. The
purpose in view, however, can be obtained by the following improved means which
also forms part of this invention.
Along the whole telephonic line of the usual construction a special escape
conductor is provided, both ends of which are connected to ground. The con-
ductor H, Figure 7, leading to ground is brought into metallic connection with the
conductor to ground G of the telephonic single lines, or, instead of two separate
ground plates, one single ground plate may be employed.
At each pole, or at as many poles as will be practicable a conductor c d leading
to ground is provided, being connected with the said escape conductor, as also with
all the insulating supports of the pole. The said escape conductor is destined to
receive the portions of current which unavoidably used to escape at the insulators,
whereby the said escaping currents are compensated, as far as is practicably
possible, and prevented from passing into the neighbouring lines.
The undue influence of electrical lines conveying electrical energy acted upon
telephonic double lines will be overcome if the telephonic lines are provided with
the improved means as before described, that is, if the insulating supports of the
telephonic line are connected by metallic conductors and if indifferent points are
established in the tops of the telephonic circuit. The portions of currents escaping
from the lines conveying energy and passing over to the telephonic double line,
will enter at equal parts into the two branches of the telephonic circuit and there
be neutralised in the tops or angle points of the circuit. But in order to further
reduce to a minimum amount the transition of portions of the current from the
conductors of energy into the telephonic lines, the insulating supports of the poles
of the line for conveying energy are connected to each other by metallic
conductors, as described with reference to Figures 2, 3 and 34 whereby the
transition is prevented.
Having now particularly described and ascertained the nature of my said inveu-
tion and in what manner the same is to be performed, I declare that what 1
claim is-
1. The improved method of preventing undue reciprocal influences between two
or more telephonic lines and between telephonic and telegraphic or other electrical
lines such as for conveying electrical energy which consists in providing metallic
conducting connections insulated from each other, between the supports of the
insulators belonging to a pole or carrier of a double or multiple telephonic line
substantially as and for the purpose set forth.
2. The method of preventing undue, reciprocal influences between two or more
telephonic lines, or between telephonic and telegraphic or other electrical lines
which consists in further providing indifferent points in the microphone coil or the
induction coil of the converter of each telephonic circuit, said indifferent points
being obtained by arranging the telephones of equal resistance at both sides of the

page_text: microphone-coil, and by adding the difference of resistance existing in the two
branches of the circuit at equal parts at both ends of the circuit, substantially as
and for the purpose set forth.
3. The method of preventing undue reciprocal influences between two or more
telephonic single lines consisting in providing metallic conducting connections
insulated from each other between the supports of the insulators belonging to a pole
or carrier of telephonic single lines and a conductor to ground provided for each
pole or carrier, said metallic connections being equally connected to the conductor
to ground of the telephonic lines and further to an escape conductor to ground
provided for the totality of the telephonic lines, substantially as and for the purpose
set forth.
4. In a telephonic double line, the combination, with the insulating supports of
the line-branches at each pole or carrier, of a metallic conductor connecting the
said supports of the two branches, substantially as and for the purpose set forth.
5. In a telephonic double line, the combination, with the insulators of each pole
or carrier belonging to the circuit, of a metallic connection carrying said insulators
and auxiliary insulators carrying the said metallic connection, substantially as and
for the purpose set forth.
6. In a telephonic line, the combination, with telephones of equal resistance
arranged at both sides of the microphone-coil, of resistances which balance the
difference of resistance between the two branches of the line-circuit, substantially
as and for the purpose set forth.
7. The combination, with two or more telephonic single lines carried by common
poles or carriers, of a conductor to ground provided for each pole or carrier, an
escape-conductor common to the totality of the lines and leading to ground, and
metallic conductors connecting the insulator-supports with said conductor to ground
and with the escape-conductor to ground and also with the line-conductors to
ground, substantially as and for the purpose set forth.
Dated this 8th day of August 1894.
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Agents for the Applicant.