Improvements in Devices for Prevention of Retardation in Electric Cables.
Year: 1893

page_text: Date of Application, 4th July, 1893
Complete Specification Left, 3rd Apr., 1894-Accepted, 12th May,
1894
PROVISIONAL SPECIFICATION.
Improvements in Devices for Prevention of Retardation in Electric
Cables.
I, SILVANUS PHILLIPS THOMPSON, of The Technical College, Finsbury, in
the County of London, Doctor of Science, do hereby declare the nature of this
invention to be as follows:-
My invention relates to electric cables for the conveyance of varying electric
impulses, and consists in developments of that set forth in my Specification
No. 22304 of 1891, in which I have described my method of counterbalancing
the retarding effects due in the ordinary kinds of electric cable to the presence of
a distributed capacity by applying distributed electromagnetic induction. Such
distributed electromagnetic induction I proposed to attain in various ways which
however fell under two general heads, namely firstly ways in which self induction
or the electromagnetic induction of a wire or coil on itself was employed,
secondly ways in which mutual induction or the electromagnetic induction of two
(or more) wires or coils upon one another was employed. In some of the cases
falling within the latter class of ways I proposed to employ suitable iron cores,
in other cases wires were used not coiled on irou cores. On page 1 line 35 of the
printed copy of the said Specification proposed to produce mutual induction
between the wires of the cables in a distributive manner without using any other
wires or coils than the wires of the cables themselves. On page 2 lines 43 to 48
I described the mutual inductive action that arises between two neighbouring
wires, an action which, being one case of electromagnetic induction is sometimes
styled electrodynamic, and on page 3 line 16 of the said Specification, I pointed
out that my invention for counterbalancing the retarding effects could be effected
by dividing or virtually dividing the entire length of the cable into sections by
the aid of devices for producing mutual induction between the parts. In Figures 2
and 3 I have shown the use of such sectional arrangements, as also in Figures 3
and 6 and others. And I have shown a virtual division into sections by the use
of self-induction coils in Figure 7, by mutual induction coils in Figure 9, and by
parallel straight wires possessing mutual induction in Figure 6.
In Figure 7 of that Specification are shown two wires each separately and
alternately connected by compensators at intervals with a third wire or with the
sheathing of the cable. In Figures 9 and 10 the two parallel wires are in sections,
or virtual sections, in mutual inductive relation and are shown as connected at
intervals alternately to a third wire or to the sheathing of the cable. On page 4
line 11 I described the induction coils as being preferably long and narrow arranged
so as not to form unwieldy enlargements.
My present invention relates to modifications of the former said invention.
In constructing the self-induction coils or devices in such a way as to avoid
unwieldy enlargements of the cable 1 employ wires of copper or iron, iron covered,
arranged in the cable parallel to the usual conductors and connected to them
suitably at intervals, and in constructing the mutual induction coils or devices
likewise I employ a third wire, preserved from mutual induction with the other
two by the interposition of windings of iron wire or similar suitable material
suitably disposed, the third wire whether continuous or discontinuous being suitably
connected at intervals with the other two wires or with either of them in such
manner as to effect the desired compensation from point to point along the cable.
In some cases I employ both the above classes of devices together in one and the
same cable. In some cases I combine devices of either or both of these classes

page_text: with the arrangements wherein in lieu of continuous conducting wires I have
employed wires or conductors in sections which overlap sufficiently to allow of
mutual induction between them. Where a third wire is employed within the
sheath I connect it variously at suitable intervals with one or other of the two
other conductors. Or where more than three wires are used in a cable, one of
them may be of iron or of wire overwound with iron, in separated sections
connected at the ends to one or other of the others, as for example where one of
them is thus connected alternately by lengths of the iron or ironclad wire to each
of the other two. Or the length of iron or ironclad wire may loop back upon
itself and be joined by its two ends to adjacent points of the two other conductors.
Or again the cable may consist of successive sections containing alternately three
conductors and two conductors suitably grouped so as to effect by electromagnetic
induction of the self or mutual kinds the desired compensation at intervals along
the length of the cable.
Dated this 4th day of July 1893.
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Devices for Prevention of Retardation in Electric
Cables.
I, SILVANUS PHILLIPS THOMPSON, of The Technical College, Finsbury, in
the County of London, Doctor of Science, 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 electric cables for the conveyance of varying electric
impulses, and consists in developments of that set forth in my Specification
No. 22304 of 1891, in which I have described my method of counterbalancing
the retarding effects due in the ordinary kinds of electric cable to the presence of
a distributed capacity by applying distributed electromagnetic induction. Such
distributed electromagnetic induction I proposed to attain in various ways, which,
however, fell under two general heads, namely, firstly, ways in which self induction
or the electromagnetic induction of a wire or coil on itself was employed; secondly,
ways in which mutual induction or the electromagnetic induction of two (or more),
wires or coils upon one another was employed. In some of the cases falling within
the latter class of ways, I proposed to employ suitable iron cores, in other cases,
wires were used, not coiled on iron cores. On page 1, line 35, of the printed copy
of the said Specification, I proposed to produce mutual induction between the
wires of the cables in a distributive manner without using any other wires or coils
than the wires of the cables themselves. On page 2, lines 43 to 48, I described
the mutual inductive action that arises between two neighbouring wires, an action
which, being one case of electromagnetic induction, is sometimes styled electro-
dynamic, and, on page 3, line 16, of the said Specification, I pointed out that my
invention for counterbalancing the retarding effects could be effected by dividing
or virtually dividing the entire length of the cable into sections by the aid of
devices for producing mutual induction between the parts. In Figures 2 and 3,
I have shown the use of such sectional arrangements, as also in Figures 3, 6 and
others. And I have shown a virtual division into sections by the use of self-induction
coils in Figure 7, by mutual induction coils in Figure 9, and by parallel straight
wires possessing mutual induction in Figure 6.
In Figure 7 of that Specification are shown two wires, each separately and
alternately connected by compensators at intervals with a third wire or with the
sheathing of the cable. In Figures 9 and 10, the two parallel wires are in sections,

page_text: or virtual sections, in mutual inductive relation, and are shown as connected at
intervals alternately to a third wire or to the sheathing of the cable. On page 4,
line 11, I described the induction coils as being preferably long and narrow,
arranged so as not to form unwieldy enlargements.
My present invention relates to modifications of the former said invention; and
consists in a number of additional detailed modes of carrying out the said former
invention, which additional detailed modes must be understood in relation to the
general features of the former invention and subject thereto.
In constructing the self-induction coils or devices referred to in my aforesaid
former Specification, and called compensators, I use such forms as will not offer
unwieldy enlargements of the cable. It is well known that even straight conductors
possess self-induction, that is to say, the current in them creates in the surrounding
space a magnetic field which gives them the property of electromagnetic inertia ;
and it is also known that a wire of iron (or other magnetic material) possesses a
higher coefficient of self-induction than a copper wire of the same gauge and
length. It is further known as a general scientific fact that a straight wire, whether
of iron or copper, possesses a greater self-induction if it is coated or overwound or
surrounded externally with iron, also that wires coiled in spirals possess higher
self-induction than straight wires, especially if they are coiled around a properly
laminated core of iron or other magnetic metal. A conductor which is so arranged,
whether by surrounding it with iron externally, or by coiling it around an iron core,
or by any other known way of giving to it a greater coefficient of self-induction
than would be possessed by a simple copper wire, I shall hereinafter call, for the
sake of brevity, a loaded conductor or a loaded wire. An insulated wire externally
overwrapped with a serving of iron wire is, for example, loaded; or, if wrapped
spirally with a tape of thin sheet iron; or if surrounded by a tube or shell of
sheet iron.
Figure 1 shows diagrammatically a cable constructed according to my invention,
having two conductors of copper, A' A2, B1 B2, of the usual type, running from
end to end, but connected together at suitable intervals by compensators or self-
inductive devices as described in my aforesaid Specification, and resembling
Figure 1 of the same, except that in the present case the compensators are not
connected across simply between two adjacent points of the two conductors, but
are connected from a point on one conductor to a point at some distance away on
the other conductor. This form permits the self-induction device to be readily
inserted in the cable, parallel to its axis without forming an unwieldy enlargement.
These devices, shown at a b, c d and e f in Figure 1, are distributed suitably along
the entire length of the cable, not necessarily at equal intervals; but always in
such way as to compensate effectively the distributive capacity of the cable and to
obviate retardations. The devices a b, c d, e f, etcetera, may, for example, consist
of greatly elongated self-induction coils consisting of many turns of fine copper
wire wound upon a very long core of straight iron wires. Or each may consist of
a coil resembling a very elongated choking-coil such as is used in electric-lighting,
but elongated perhaps to hundreds of yards or more in length, the elongated coil
consisting of one or more turns of insulated wire of copper or iron or other metal,
one or both of the limbs of the loop being overwound with fine iron wire, as
indicated in Figure 2 or in Figure 3, to increase the self-induction, and load the
wire. Or the compensator a b may consist of a straight iron or iron clad wire
some miles in length, as in Figure 4, where the spiral line surrounding the wire a b
indicates the external loading of iron; or to secure greater self-induction, it may
consist of an iron or iron clad wire, wound in a single spiral upon a suitably
insulated straight iron wire, as core, as indicated in Figure 5. It will be under-
stood that all these forms are self-induction devices suitable to be used as compen-
sators and for diagrammatic purposes are sufficiently indicated in general by a spiral
line, such as a b in Figure 1.
Another way of arranging the compensators across the cable is shown in
Figure 6, where the connections of the longitudinally placed devices are alternated,

page_text: as compared with Figure 1. If each compensator is sufficiently elongated, the end
of one, as at b, will extend near to the beginning, c, of the next. An obvious step
from this construction leads to that depicted in Figure 7, wherein is shown a cable
having, in addition to the two ordinary copper conductors A' A2, B1 B2, a third
wire parallel to the other two, this third wire being a loaded wire connected to the
other two at suitable intervals alternately so as to secure, between any one point
on the one conductor and any point on the other conductor, the action of an
inductive shunt having both a sufficiently high time-constant and a sufficiently high
resistance as set forth in my aforesaid former Specification. The windings of iron
overwrapped upon the loaded wire, if constructed on the plan indicated in Figure 4,
will not only have the effect of increasing its self-induction but also for preserving
it from mutual induction which otherwise might take place between it and either
of the other two conductors if no iron or magnetic material were interposed
between it and them. Figure 8 is a diagram in section of such a cable, but
does not show the alternate connections every few miles between A and C and
between B and C ; C being the loaded wire; and S indicates the external iron
sheathing. The same end is practically attained by wrapping iron around the
two conductors A¹ A and B B together, and placing the third compensator
wire outside this wrapping and between it and the external iron sheathing of
the cable, in which position it will be practically surrounded with iron on one
side or the other, thereby loading it. This latter deposition is indicated in Figure 9.
A serving of tape of thin sheet iron around the two conductors not only effects
this purpose, but also performs the service of protecting them against the attacks
of the teredo.
In like manner, in constructing the mutual-induction devices, for operating as
set forth in my aforesaid former Specification, I, in some cases, employ elongated
two-wire induction coils, each like a greatly extended "shell transformer" such as
is indicated in Figure 10, wherein the loop a b is brought into mutual induction with
the loop cd by being laid alongside and overwrapped with iron or similar magnetic
material. In Figure 11 is shown another form of mutual induction device whereby
two long loops a b and c d are brought into inductive relation by being provided
with a suitable wrapping or sheathing of iron around two of the four parallel
parts, instead of two such wrappings as in Figure 10.
An example of the mode of using mutual-induction devices according to my
aforesaid former invention is shown in Figure 12, where one of the two con-
ductors AA is actually cut up into separate lengths, which are inductively
connected together by the mutual induction coils arranged so that the currents in
the successive loops or sectional circuits circulate in opposite senses, as is indicated
by the arrows. Figure 13 depicts an alternate arrangement, in which both the
conductors A' A² and B' B2 are divided at intervals. It is obvious that the
currents in each of the successive sectional circuits will be of less strength than in
the preceding one, the excess of current in the first circuit over that in the second
being approximately a measure of the amount required to compensate the
retardation at that part of the cable, and so forth. It is in these cases very
important that the device used for mutual induction should have as little magnetic
leakage as possible, that each of the two wires of the mutual-induction device
may have little or no unbalanced self-induction. In the construction of cables
with mutual induction devices, I also employ in some cases, as I did in Figures 9
and 10 of my said former Specification, a third wire connected at intervals
alternately with the other two. This third wire, whether continuous or discon-
tinuous, may be preserved from mutual induction with the other two by the
interposition of suitable over-windings of iron wire or the like magnetic
material properly disposed. Such dispositions amount to a combined use of mutual-
induction devices with self-induction devices. For example, Figure 14 shows the
two conductors A¹ A2, B1 B2, brought into mutual induction with one another at
intervals distributively, in the manner indicated in Figure. 3 of my said former
Specification, whilst at the same time they are connected by self-induction devices

page_text: or compensators at a b, c d, and e f to a third wire C C³, alternately in the way
indicated in Figure 7 of my said former Specification. In this case, the metallic
sheath of the cable may be used as third wire C¹ C², but if not, it is evident
that CC may itself also be a loaded wire. Figure 15 is a simple modification of
the preceding arrangement, wherein the loaded wire C¹ C² acts in sections as
compensators across the two conductors A' A' and B' B²; for example, the
section of C¹ C' from 6 to d acts as a self-induction compensator connected across
the cable from a to c. If, to carry out these two latter arrangements of Figures 14
and 15, the distributed electromagnetic inductions, both self and mutual, are
obtained by overwrapping the conductors with iron wire externally, the sections
of cable so constructed will be diagrammatically represented by Figures 16
and 17, whereof Figure 16 corresponds to a section at M N on such a cable as is
represented in Figure 14 and Figure 17 to a section at M N in Figure 15.
It is not necessary for A' A² and B' B2 to be continuous, provided that they
are brought into suitable mutual inductive relations from section to section.
Thus, in Figure 18, the conductors A¹ A² and B1 B2 are each at intervals
connected to a third wire C₁ C2 which is loaded with a suitably distributed self-
induction. The cable constructed in accordance with this plan will consist of
portions of a three-wire cable, such as is diagrammatically represented in
Figure 17, Figure 9, or Figure 8, connected together suitably at intervals by
pieces of simple two-wire cable. Another arrangement is shown in Figure 19, in
which the successive sections of the two main conductors are inductively connected,
as in Figure 10, to one another, and the several sectional circuite are
compensated by being alternately connected to the wire C, which, in this case,
may be either a simple or a loaded wire; so constituting, as shown in diagram in
Figure 20, which is virtually a section of Figure 19 at MN, a five-wire cable.
In this case, the ordinary external metallic sheathing of the cable may be used
instead of the wire C. In Figure 21 is shown another modification in which the
mutual induction devices are of the type shown in Figure 11, the several sectional
circuits A² B¹, A² B³, A³ B³, etcetera, being, as before, cross-compensated by being
connected to the wire C1 C2 at intervals. A section through this cable at M N is
represented in diagram by Figure 22.
cross-
As mentioned in my aforesaid former Specification, it is not necessary in all
cases to use closed circuits, since two conductors, in no way joined together but
merely lying side by side, may have mutual induction between them if they
overlap sufficiently. In devices of this kind, which resemble unclosed induction
coils or
"phonopores," the mutual induction will of course be increased by the
application of properly disposed iron to increase the electromagnetic action.
For example, a mutual induction device may be arranged, consisting, as in
Figure 23, of two insulated straight wires of copper A' and A2 lying side by side,
each having one free end, both being overwound together with a wrapping or
sheathing of iron to increase the mutual induction. Figure 24 represents a cable
constructed with a series of such devices, the conductors A'A' A³, etcetera, which
constitute the overlapping wires in the devices, being connected at intervals, as
at a, c and e, to a loaded third wire C¹ C². Or C' C² may be simply a straight
third wire, provided the connecting pieces ab, cd, ef, etcetera, are themselves
compensators or loaded conductors as in Figures 1, 2, 3 and 4 and 5, described
above. It is obvious that Figure 24 may be constructed as a three-wire cable
with a section at M N resembling Figure 17 or Figure 9; the connections at the
proper intervals being of course rightly made. Figure 25 and Figure 26 relate to
cables containing two copper conductors A and B, which, by running side by side
within the external iron sheathing of the cable, or within some special over-
wrapping of iron, are in mutual inductive relations to one another practically
continuously throughout their whole length. In Figure 25 they are connected at
intervals to a third wire C, which must be shielded from mutual inductive relations
with them by the interposition either of its own iron overwrapping, or of theirs.
It will be seen that, in this figure, the successive sections or portions of C

page_text: act as inductive shunts or compensators connected across from the A. conductor
In all
to the B conductor at some point at a distance along the cable.
cases where the two conductors A and B are in mutual inductive relation
to one another between the points where A is connected to C and where B is
connected to C, there is less need to prescribe that the part of C which is connected
across shall have either a high time-constant or a high resistance; such is
necessary in all cases where the two ends of the compensator are joined to the
A and B lines at points close together as in several cases in my former Specification.
Figure 25 does not exhibit, by any spiral lines, that there is a distributive mutual
induction all along between the A and the B conductors, neither does it indicate
that C is a loaded wire. It is electrically the equivalent of Figure 15 in which
spirals are used to indicate both these features. It is also true of Figures 14, 15,
18, 19 and 21 that the greater the mutual induction between the A and the
B conductors, the less need will there be to make C of great resistance or great
.self-induction. Figure 25 is a diagram of a three-wire cable such as Figures 8, 9
or 17 in section. Figure 26 also relates to cables having the A and the
B conductors in a practically continuous mutual inductive relation; but having the
third or compensating wire applied across only at intervals from the A conductor
to some point on the B conductor further along, so that there is a mutual induction
between A and B between the two points which are respectively joined to the two
ends of each compensating wire C. In this case, therefore, also the C wires need
not have either high time-constants or high resistances. And the construction of
the cable will consist of alternate portions of a three-wire cable such as indicated
in Figures 8, 9 and 17, and of a two-wire cable of the ordinary sort, or else of a
two-wire cable with a special over-wrapping or sheathing of iron to increase
electromagnetically the mutual induction between them. have described these
constructions of cable as suitable for telephony and rapid telegraphic signal; but
it is self evident that the same properties will render them suitable for the
transmission of rapidly-varying electric impulses, for whatever purpose.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. In an electric cable for transmitting rapidly varying electric impulses having
two continuous principal conductors, the combination of mutual induction devices
between the said two principal conductors with self induction devices (or
compensators) arranged as shunts across the cable from the one principal conductor
to the other.
2. In an electric cable having two principal conductors and having devices for
producing mutual induction between the said two principal inductors distributively
along the length of the cable, the combination of the said conductors that are in
mutual inductive relations to one another with compensators or wires possessing
both self induction and resistance, the said compensators being each connected as a
shunt from a point on one of the said principal conductors to a point further along
on the other principal conductor.
3. The application in electric cables containing two conductors in mutual
inductive relation to one another, of shunts to which an augmented self induction
is given by coating, overwinding or enclosing them with iron or other magnetic
material, or by coiling them in spirals, substantially as described.
4. In an electric cable the use of elongated selt induction devices substantially
as described with reference to Figures 2 to 5.
5. An electric cable containing three conductors whereof two are ordinary
conductors of copper, and the third a wire of higher resistance connected at
intervals alternately to the other two, substantially as and for the purposes
described.
6. An electric cable containing three conductors whereof two are ordinary
conductors of copper, and the third a wire of iron having resistance & self

page_text: induction substantially as described and being connected at intervals alternately to.
the other two.
7. An electric cable containing three conductors whereof two are ordinary
conductors of copper, the third being a wire of augmented self-induction obtained
by overwinding it with iron or otherwise, the same being connected at intervals.
alternately to the other two substantially as described.
8. An electric cable containing three conductors, two of them being principal or
ordinary conductors of copper, the same being enclosed for the purpose of
augmenting their mutual induction by a suitable external wrapping of iron or
similar magnetic material constituting an internal inductive sheathing, the third
wire being outside the said wrapping or inductive sheathing.
9. In an electric cable the combination of two copper conductors running
continuously through the cable from end to end, each separately insulated, with
an external serving or wrapping of thin strip or tape or wire of iron, whether
connected at intervals to any other wire or not, all being within the outer ordinary
protective sheathing.
10. In au electric cable the combination of two principal conductors which are
together overwound or covered with iron to augment their mutual induction, with
a third wire lying parallel to them the same being also overwound or covered with
iron to augment its self induction.
11. In an electric cable having two principal conductors, the same not being
continuous throughout but divided into sectional circuits which are in mutual
inductive relations to one another, the combination of such sectional circuits with.
self inductive shunts the ends of which are connected respectively to points on.
two adjacent sections substantially as in Figure 21.
12. In an electric cable having two principal conductors, the same not being
continuous throughout, but divided into sectional circuits, which are in mutual
inductive relations to one another, the combination of such sectional circuits with
a third wire to which the said sectional circuits are alternately connected.
substantially as shown in Figure 19.
13. In an electric cable, the use of elongated mutual induction devices substan-
tially as described with reference to Figures 10 and 11.
14. In an electric cable the use of non closed mutual induction devices substan--
tially as shown in Figures 23 and 24.
15. An electric cable having two principal conductors of copper in mutual
inductive relations with one another, a third wire self inductively loaded and
divided into sections, and a fourth wire that is continuous, constituting a four wire
cable as shown in section in Figure 16 and connected substantially as in Figure 14..
16. An electric cable consisting of alternate lengths of three wire cable such as
is shown in section in Figures 8, 9 or 17, and of two wire cable, the successive.
lengths being connected together, and having their respective conductors connected
substantially as is shown in Figure 18.
17. The arrangements of five wire cables substantially as shown in Figures 20.
and 22.
18. The arrangements of three wire cables substantially as described with
reference to Figure 25.
19. The arrangement of successive lengths of three wire and of two wire cable
joined together substantially as described with reference to Figure 26.
Dated th: 0-1
J
A
1004
WM. P. THOMPSON & Co.,
Of Liverpool, Manchester, Nottingham, and London, Patent Agents.