An Improvement in Telephone Cables.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
An Improvement in Telephone Cables.
I, LLEWELLYN TRAHERNE BASSETT SAUNDERSON, of 10, De Vesci Terrace,
Kingstown, County Dublin, Ireland, Gentleman, do hereby declare the nature
of this invention to be as follows:-
My invention has for its object to shield the conducting wires of an aerial or
subterranean telephone cable in such manner as to prevent them from being
influenced inductively by currents flowing in neighbouring conductors or other-
wise, and thus to avoid the production of the murmuring or buzzing noises
perceptible when the wires are subjected to such inductive influence."
The invention consists in enclosing the two wires, or each separate wire of a
circuit within a completely tubular continuous metallic armouring of such
minute thickness as not to interfere with the necessary flexibility of the cable,
and in putting the two ends of this sheathing to earth so that all induction cur-
rents from external sources, which would otherwise influence the contained
wire or wires, will be intercepted and conveyed to earth.
This conductive armouring may be of copper, tin, or other metal and applied
externally of the insulating covering of the wire, either by electro-deposition
or in the form of foil or very thin tape, the foil or tape when of tin or other metal
less conductive than copper, being electro-coppered if required in order to
increase its conductivity.
a fine
To guard against the interruption of the continuity of the sheathing
wire is wound in long spirals around the deposited coating so as to bridge over
any fracture of the latter, the whole being being enclosed in, and protected by,
the usual outside covering of the cable.
A. M. & WM. CLARK,
Chartered Patent Agents, 53, Chancery Lane, London.
An Improvement in Telephone Cables.
I, LLEWELLYN TRAILERNE BASSETT SAUNDERSON, of 10, De Vesci Terrace,
Kingstown, County Dublin, Gentleman, 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 has for its object the shielding of the conducting wires of an
aerial or subterranean telephone cable in such a manner as to prevent them
from being influenced inductively by currents flowing in neighbouring con-
ID037

page_text: 2
ductors or otherwise, and then to avoid the production of the murmuring or
buzzing noises or interference with the clear articulation of the transmitted tele-
phonic message, which often occurs when the conducting wires are subjected to.
inductive influence.
The invention consists in enclosing the two wires, where a metallic return is
used, of a telephonic circuit, within a complete metallic shield of such con-
formation or minute thickness as not to interfere with the necessary flexibility
of the cable, the ends of such shield or metallic sheathing being put to earth
in any convenient sections so that all induction currents from external sources,
which might otherwise be set up in the telephonic conductor will be intercepted
by the said shield or metallic sheathing and conveyed to earth.
The internal conducting wires of the telephonic circuit are protected in the
usual manner by any insulation, so that there is no metallic contact between
the telephonic circuit and the external metallic induction shield, the whole
being enclosed and protected by a usual outside covering of the cable.
The conductive shield may be of copper or of any other metal of good con-
ducting properties, and to maintain flexibility of the finished cable may be
applied as a continuous strip of foil wound spirally around the telephonic insu-
lated conductors, the spirals overlapping upon one another, and continuity in
case of fracture being safe-guarded, if necessary by a fine wire being wound
round the said shield or sheathing in spirals.
Electro-deposition may be used if desired for the formation of the metallic
shield or for increasing the conductivity of the foil if the latter is not of good
conductivity.
In order that my invention may be better understood I now proceed to show
diagramatically a portion of a shielded telephonic circuit according to my inven
tion as an illustration of one mode of carrying the same into effect.
A, A¹ are the direct and return wires of a metallic telephonic circuit. These
wires arc insulated by any suitable coating B in the usual way.
About the two wires I wrap a metallic shield C in the form preferably of a
strip of copper foil wound spirally about the said wires, the spirals overlapping
upon themselves.
The said strip or shield C is put on earth at E, E, at any suitable intervals
and the whole cable is covered by the usual protective coating D.
It is obvious that where the individual circuits are thus shielded a number of
shielded circuits can be safely brought together in one cable as in Fig. 2 the
shields being all connected to one earth connection at each end in suitable
sections.
Having now particularly described and ascertained the nature of the said in-
vention and in what manner the same is to be performed I declare that what
I claim is:-
In a telephonic cable the combination with an insulated telephonic conductor
or conductors of a metallic enveloping shield, adapted by its form or mode of
application, not to impair the flexibility of, nor to add greatly to the weight
of the cable, and connected at either end to earth, in suitable sections, to pro-
tect the said telephonic conductors from the inductive action of external elec-
trical currents, substantially as described.
Dated this 6th day of January 1899.
FELL & JAMES,
Agents for the Applicant,
1, Queen Victoria Street, London, E.C.