IMPROVEMENTS IN AND RELATING TO THE NEUTRALIZATION OF INDUCED CURRENTS CAUSED IN TELEGRAPH AND TELEPHONE LINES BY CURRENTS IN OTHER LINES ATTACHED TO THE SAME POSTS OR SUPPORTS
Year: 1881

page_text: PROVISIONAL SPECIFICATION left by William Phillips Thompson at the
Office of the Commissioners of Patents on the 8th June 1881. A communi-
cation from abroad by François Van Rysselberghe, of Brussels, in the Kingdom
of Belgium.
WILLIAM PHILLIPS THOMPSON, of the Firm of W. P. Thompson and Co., Agents
for Foreign Patent Solicitors, of 6, Lord Street, Liverpool, in the County of
Lancaster, and of 323, High Holborn, in the County of Middlesex, Civil Engineer.
" IMPROVEMENTS IN AND RELATING TO THE NEUTRALIZATION OF INDUCED
CURRENTS CAUSED IN TELEGRAPH AND TELEPHONE LINES BY CURRENTS IN
OTHER LINES ATTACHED TO THE SAME POSTS OR SUPPORTS." A communication
from abroad by François Van Rysselberghe, of Brussels, in the Kingdom of
Belgium.
The following is a literal translation of the Specification as sent to me by my
firm's Brussels correspondent with orders to file.
I have found by experience that the induced currents in question net as though
they proceeded from an electromotive force with an interior resistance relatively
feeble, since they are rapidly extinguished when one opposes to them considerable
and increasing exterior resistances. Take, for instance, a circuit connecting two
posts A and B and composed as follows:-First, on post A one or several coils for
the emission of induced currents; second, on post B one or several coils for the
reception and utilization of these currents; third, the line between these posts.
If one gives to the coils of emission as well as to the coils of reception an
enormous resistance so considerable that the resistance of the line can be almost
neglected in the calculation, the induced currents caused in this line by the currents
of neighbouring lines are no longer in a condition to influence the receptive system
in a pernicious degree. These currents are extinguished and lost in the great
resistance of the entire circuit. Only the currents emitted by the generating coils
on post A act efficaciously on the reception coils on B; they can even cross (in
these conditions) enormous distances. The interposition of a strong complementary
resistance in the circuit can still further aid to attain this end.
This principle has, I believe, never been utilized for the purpose specified above,
or even been suggested up to the present. It will be found specially useful in the

page_text: case of telephones in preventing the discordant noises which are actually produced
in these instruments by the induction from other wires in the same cable or set
of lines.
The Invention may be briefly summed up as follows:-
-
The induced currents in the lines are practically neutralized by giving a resistance
to the reception coil enormously greater than the line resistance, instead of tho two
being equalized, as is now the practice.
This is done by multiplying the coils, or greatly increasing the length of the
wires on the coils, or substituting wire of greater resisting qualities, such as iron
or steel, for the copper wire usually employed.
This greatly increased resistance kills the induced currents, or rather prevents
their occurrence, only the line current having strength to conquer the resistance of
the coil.