Method of Increasing the Speed of Signalling in Submarine or Subterranean Cables, and the Construction of such Cables for this Purpose.
Year: 1892

page_text: Date of Application, 28th Oct., 1892
Complete Specification Left, 20th July, 1893-Accepted, 26th Aug., 1893
PROVISIONAL SPECIFICATION.
Communicated from abroad by Messrs. SIEMENS & HALSKE, of 94, Markgrafen
Strasse, Berlin, in the German Empire.
Method of Increasing the Speed of Signalling in Submarine or
Subterranean Cables, and the Construction of such Cables for
this Purpose.
We, SIEMENS BROTHERS & COMPANY LIMITED, of 12, Queen Anne's Gate,
Westminster, in the County of Middlesex, Electrical Engineers, do hereby declare
the nature of this invention to be as follows:-
As is known, the speed with which telegraphic messages can be transmitted
through long submarine cables, is diminished in cables of identical construction,
inversely as the square of their length. This increase of retardation can be
obviated by increasing the size of the conductor and the thickness of the insulating
coating of the cable, but the cost of a long cable is thereby very greatly
augmented.
There exists consequently at present a practical limit to the length of a
submarine cable, on exceeding which the undertaking becomes an unprofitable one.
The present invention relates to a method by means of which a cable of equal
construction can be made more than half as long again without decreasing the
signalling power.
It is well known that this object can be attained by the introduction of electro-
magnetic translating stations as has already been effected by us with the best
results in the first long cable from Suez to Aden in the year 1859. This requires
however the existence of fixed points for the erection of the necessary instruments.
The sinking of a so called relay translator at the middle of the cable, by which
the problem could be solved, cannot be carried out, as such an apparatus will not
work continuously without regular supervision.
The present invention consists in replacing the relay translator by an electro-
dynamic or Volta inductor of suitable construction.
The cable is for this purpose divided in the middle, and each end is connected to
one of the two circuits of the inductor.
The free ends of the same are connected to earth.
Fig. 1 of the accompanying drawings shews a diagram of this arrangement
where A A are the two lengths of cable, the inductor, Ca battery D a condenser,
and E E earth connections.
The cable thus divided consequently forms two separate conducting circuits, that
are only connected with each other to the extent that the current flowing through
one part of the conductor of one circuit is made to act inductively upon a part of
the conductor of the other circuit. Each current impulse starting from the one
end station must consequently produce a correspondingly strong induced current at
the other end station, which can be used for signalling. As the individual circuits
have only half the length of the cable, the retardation due to the charging of the
condenser constituted thereby will only be only be one fourth of that due to a cable of
the entire length, and consequently the speed of transmission will be the fourfold of
that attainable in a cable of the entire length.
Owing to the retarding influence of the resistance of the receiving instruments
and to the increase of the actual length of the entire conductor by the introduction
of the inductor wires, the said quadruple speed, which should be obtained
theoretically, will no doubt in practice be generally reduced to about double the
sneed

page_text: The described introduction of a Volta inductor into the cable is however subject
to practical difficulties. We therefore prefer to effect the induction in the following
manner.
A portion of the cable near the middle of the length is made as a twin cable,
that is to say, there are provided in the insulating gutta percha covering two
copper wire strands or conductors insulated from cach other and if necessary
arranged concentrically to each other.
The opposite ends of this twin conductor are so connected with the single
conductors of the other parts of the cable that each of the double conductors forms
the end of one of the single conductors.
This arrangement is shewn at Fig. 2. The double cable B therefore acts as
inductor, each of its wire strands performing the function of one of the two inductor
coils, the iron sheathing which surrounds the cable being made to produce a
strengthening action corresponding to that of the iron core of the inductor. The
free ends of the twin conductors are connected with the iron sheathing, and
consequently with earth.
This form of construction for carrying out the said invention can be readily so
carried out that the cable can be laid without the slightest danger to this operation
or to the reliable working.
Induced currents may also be used in the charging part of the cable in place of
the usual battery double currents, if circumstances should render this desirable.
Instead of dividing the cable into only two parts, it may be divided into a
greater number of parts, and induction apparatus or twin conductors be introduced
at each point of division, in the manner above described.
This would be advisable when the cable is to be used for telephonic transmission.
In some cases we construct the entire cable with twin conductors and we connect
these conductors alternately at regular intervals with earth. This arrangement
may be advantageously employed in particular for subterranean conductors that are
employed for telephonic transmission.
Fig. 3 shews this arrangement, A. A being the two conductors, E E the earth
connections and F the telephonic instruments.
Dated this 28th day of October 1892.
ABEL & IMRAY,
Agents for the Applicants.
COMPLETE SPECIFICATION.
Method of Increasing the Speed of Signalling in Submarine or
Subterranean Cables, and the Construction of such Cables for
this Purpose.
We, SIEMENS BROTHERS & COMPANY LIMITED of 12 Queen Anne's Gate,
Westminster in the County of Middlesex, Electrical Engineers, 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 :-
As is known, the speed with which telegraphic messages can be transmitted
through long submarine cables, is diminished in cables of identical construction,
inversely as the square of their length. This increase of retardation can be
obviated by increasing the size of the conductor and the thickness of the insulating
coating of the cable, but the cost of a long cable is thereby very greatly
augmented.
There exists consequently at present a practical limit to the length of a
submarine cable, on exceeding which the undertaking becomes an unprofitable one.
The present invention relates to a method by means of which a cable of equal
construction can be made more than half as long again without decreasing the
signalling power.

page_text: It is well known that this object can be attained by the introduction of electro-
magnetic translating stations as has already been effected by us with the best
results in the first long cable from Suez to Aden in the year 1859. This requires
however the existence of fixed points for the erection of the necessary instruments.
The sinking of a so called relay translator at the middle of the cable, by which
the problem could be solved cannot be carried out, as such an apparatus will not
work continuously without regular supervision.
The present invention consists in replacing the relay translator by an electro-
dynamic or Volta inductor of suitable construction.
The cable is for this purpose divided in the middle, and each end is connected
to one of the two circuits of the inductor.
The free ends of the same are connected to earth.
Fig. of the drawings accompanying our Provisional Specification shews a
diagram of this arrangement where A A are the two lengths of cable, B the
inductor, C a battery, D a condenser, and E E earth connections.
The cable thus divided consequently forms two separate conducting circuits, that
are only connected with each other to the extent that the current flowing through
one part of the conductor of one circuit is made to act inductively upon a part of
the conductor of the other circuit. Each current impulse starting from the one
end station must consequently produce a correspondingly strong induced current
at the other end station, which can be used for signalling. As the individual
circuits have only half the length of the cable, the retardation due to the charging
of the condenser constituted thereby will only be one fourth of that due to a cable
of the entire length, and consequently the speed of transmission will be the four-
fold of that attainable in a cable of the entire length.
Owing to the retarding influence of the resistance of the receiving instruments
and to the increase of the actual length of the entire conductor by the introduction
of the inductor wires, the said quadruple speed which should be obtained
theoretically, will no doubt in practice be generally reduced to about double the
speed.
The described introduction of a Volta inductor into the cable is however subject.
to practical difficulties.
We therefore prefer to effect the induction in the following manner.
A portion of the cable near the middle of the length is made as a twin cable,
that is to say, there are provided in the insulating gutta percha covering two
copper wire strands or conductors insulated from each other and if necessary
arranged concentrically to each other.
The opposite ends of this twin conductor are so connected with the single
conductors of the other parts of the cable that each of the double conductors
forms the end of one of the single conductors.
This arrangement is shewn at Fig. 2. The double cable B therefore acts as
inductor, each of its wire strands performing the function of one of the two
inductor coils, the iron sheathing which surrounds the cable being made to produce
a strengthening action, corresponding to that of the iron core of the inductor.
The free ends of the twin conductors are connected with the iron sheathing and
consequently with earth.
3
This form of construction for carrying out the said invention can be readily so
carried out that the cable can be laid without the slightest danger to this operation
or to the reliable working.
Induced currents may also be used in the charging part of the cable in
place of the usual battery double currents, if circumstances should render this
desirable.
Instead of dividing the cable into only two parts it may be divided into a greater
number of parts and induction apparatus or twin conductors be introduced at each
point of division, in the manner above described. This would be advisable when
the cable is to be used for telephonic transmission.
In some cases we construct the entire cable with two conductors and we connect

page_text: these conductors alternately at regular intervals with earth. This arrangement
may be advantageously employed in particularly for subterranean conductors that
are employed for telephonic transmission..
Fig. 3. shews this arrangement, A A being the two conductors, E E the earth
connections and F the telephonic instruments.
We are aware that it has been proposed to divide cables containing twin or
multiple insulated conductors and to form each section into a closed metallic
circuit including a compensator for counteracting the effect of static induction, and
we make no claim to such an arrangement.
Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed, we declare that what we
claim is :-
1. In submarine or subterranean cables having a circuit completed by earth, the
method of increasing the speed of signalling by dividing the cable into sections,
and providing each section with means whereby a signalling current sent through
the one section is made to produce an induced current in the contiguous section
and is then put to earth, substantially as described.
2. The construction of cables for carrying out the method referred to in the
first claim wherein an electromagnetic induction apparatus having two windings is
so connected to the two separated sections of a cable, that while the one winding
has its one end connected to the one cable section and its other end to earth, the
other winding has its one end connected to the second cable section and its other
end to earth, substantially as described with reference to Fig. 1 of the drawings.
3. The construction of cables for carrying out the method referred to in the
first claim wherein there are arranged at one or more symetrically situated points
of the cable a length of double cable consisting of two parallel conductors
insulated from each other within one and the same core, the one such conductor
being connected at one end to the one cable section and at the other end to earth,
while the other such conductor is connected at the one end to the other cable
section and at the other end to earth, substantially as described with reference to
Fig. 2.
4. The construction of cables for carrying out the method referred to in the
first claim wherein two separate conductors are laid side by side in the cable, the
one conductor being connected at one end to the signalling apparatus at the one
end station and at symetrically arranged points of its length to earth while the
other conductor is connected at one end to the signalling instruments at the other
end station, and, at points arranged intermediately between those of the other
conductor, with the earth, so that each conductor of the cable thus forms a separate
electrical circuit substantially as described with reference to Fig. 3.
Dated this 20th day of July 1893.
ABEL & IMRAY,
Agents for the Applicants.