Improvements in Means for use in or in connection with the Con- veyance of Varying Electric Impulses, applicable to Electric Signalling for Telegraphic, Telephonic, or other Purposes.
Year: 1891

page_text: Date of Application, 21st Dec., 1891
Complete Specification Left, 21st Sept., 1892-Accepted, 26th Nov., 1892
PROVISIONAL SPECIFICATION.
Improvements in Means for use in or in connection with the Con-
veyance of Varying Electric Impulses, applicable to Electric
Signalling for Telegraphic, Telephonic, or other Purposes.
SILVANUS PHILLIPS THOMPSON of the Technical College, Finsbury, London
Doctor of Science do hereby declare the nature of this invention to be as
follows:-
My invention pertains to electric signalling for telegraphic, telephonic or other
purposes, and in general to the transmission of varying electric impulses through
long lines or cables and has for its chief objects to extend the distance to which
such signalling can be carried on and to increase the rapidity and facility of
signalling.
These objects I effect by special constructions of lines and cables or by special
adaptations to existing types of lines and cables. The presence in lines and cables
of electrostatic capacity limits the rate of signalling and the distance of signalling
as well as limiting the kinds of signals that can be transmitted to a given distance.
Such electrostatic capacity is in general not located at any one point but is
The method
distributed more or less uniformly along the line, cable or circuit.
common to all my various plans for carrying out my invention consists in counter-
balancing the effects of this distributed capacity by applying distributed electro-
magnetic induction. In some of my plans of counterbalancing the electrostatic
capacity this is effected by introducing at intervals into the lines or cables, or at
more or less frequent points along the length of the lines or cables, organs
possessing electromagnetic induction of amounts sufficient more or less completely
to balance the distributed capacity, bearing in mind the average frequency of the
electric impulses, whether telegraphic telephonic or other, which are to be trans-
mitted. In other plans an electromagnetic induction is distributed more or less
uniformly along the lines or cables; such plans involving lines or cables of special
construction. In the case of concentric cables or cables with two or more con-
ducting circuits within them! make use either of self-induction coils, or of mutual-
induction coils, or of combinations of these, such coils being with or without
cores of magnetic materials such as iron, or I make use of such magnetic materials
to promote the electromagnetic induction of the lines or cables themselves, either
at intervals or in a more or less continuous and uniformn manner, some or these
plans being more suitable in some cases and some in others, but always with such
use of electromagnetic induction as shall at least approximately counterbalance the
effects of capacity. Where the effects of capacity are likely to be increased by
time or change of weather 1 preferably so provide that the electromagnetic
induction shall somewhat overbalance such effects under normal conditions. In
one of my plans 1 produce mutual induction between the wires of the cables in a
distributed manner without using any other wires or coils than the wires of the
cables themselves.
Where self-induction coils are used at intervals along cables of ordinary con-
struction they are inserted as shunts across the circuit but always at such intervals,
of such size, and in such wise as shall fulfil the condition of approximate balance
common to all my said plans. Where cables containing a pair of wires for a circuit
are employed, produce approximate balance of the electrostatic capacity between
them by augmenting their mutual induction by the use of iron wire pieces within the
outer sheathing.
Dated this 20th day of December 1891.

page_text: COMPLETE SPECIFICATION.
Improvements in Means for use in or in connection with the Con-
veyance of Varying Electric Impulses, applicable to Electric
Signalling for Telegraphic, Telephonic, or other Purposes.
1, SILVANUS PHILLIPS THOMPSON, of the Technical College, Finsbury,
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 pertains to electric signalling for telegraphic, telephonic or other
purposes through long lines or cables, and has for its chief objects to extend the
distance to which such signalling can be carried on and to increase the rapidity and
facility of signalling.
66
By signalling," I mean the communicating of any sort of signals, whether
spoken words, as in telephonic signalling, or humming sounds, as in harmonic
telegraphs, or rapidly-reversed impulses like those used in rapid automatic
telegraphy, or dot and dash signals due to interruptions or reversals of current, or
deflections of a needle to right and left or motions of a siphon recorder or of the
tongue of a relay.
As lines and cables whether aerial, subterranean or submarine are now con-
structed, there is a practical limit to the distance to which signalling is possible
with existing instruments: my invention will increase this distance. There is,
also, for a line or cable of given length, as at present constructed, a limit to the
rapidity at which signals can be transmitted by instruments of a given type; my
invention will increase this rapidity of signalling. There is moreover, for a line
or cable of given length as at present constructed, a limit to the kind of instru-
ment that can be used to signal, high speed instruments, harmonic telegraphs and
telephones not being capable of being used on long cables or on very long lines:
my invention will extend the facility of signalling by rendering lines and cables
available for instruments for which they are not now available. It will also increase
the facility of signalling through submarine cables by enabling signalling to be
carried on without such expensive arrangements for securing balance, known as
artificial cables, as at present used at the shore ends.
It is known that the presence in cables and lines of electrostatic capacity limits
the rate of signalling and the distance of signalling, as well as limits the kinds
of signals that can be sent to a given distance. For example, the capacity of
an Atlantic cable, which is about microfarad per nautical mile, retards telegraphic
signals so much that only a few words per minute can be transmitted.
distance to which rapid automatic signals can be sent through cables of this type is
but a few score miles. Through very long cables of existing types, telephones,
harmonic telegraphs and rapid automatic instruments cannot be used at all.
The
It is known that the cause of the limitations mentioned above as found with
cables and long lines of existing type is the presence throughout the length of
the cable of electrostatic capacity. Such electrostatic capacity is in general not
located at any one point, but is distributed more or less uniformly along the line
or circuit.
Now, by my invention, I counterbalance the effects of this distributed capacity by
applying distributed electro-magnetic induction. Electro-magnetic induction is
the action which the rise or fall of the current in any part of the circuit produces
on the same or any other part of the circuit by virtue of the fact that every
varying current produces around it a varying magnetic field. When the current
is varying in a wire or coil, the varying magnetic field around it induces electro-
motive forces in neighbouring conductors or coils or in other convolutions of the
same wire or coil. By proper dispositions as hereinafter further described, such

page_text: electro-magnetic induction, if suitably distributed along the cable or line, may be
utilised to diminish, or even to neutralise for all effective purposes, the retarding
and limiting effects of distributed electrostatic capacity. Under the most favourable
dispositions, practically the whole of the electrostatic capacity is counterbalanced
and then the retarding and limiting effects will be neutralised: where the conditions
or arrangements are less favourable, a part only of the electrostatic capacity will
be counterbalanced, and, in such cases, the retarding and limiting effects, though
not entirely neutralised, will be diminished. When the arrangements are such as
to thus balance the distributed capacity, and neutralise the retarding effects, then
the system will conduct like any ordinary plain conductor, the current shunted off*
through the compensators following the ordinary laws of current flow.
My present invention consists in dividing the entire line into sections of prefer-
ably equal resistance, and between each section inserting an induction device
capable of more or less completely neutralising the electrostatic charge of a portion
of the line equal to one section. It can be effected by dividing, or virtually
dividing, the entire distance through which the signals have to be sent into separate
circuits by the aid of devices for producing mutual induction between the parts, or
by introducing into the entire circuit at intervals what I may term compensators,
possessing electro-magnetic induction, sufficient more or less completely to balance
the distributed capacity, bearing in mind the average frequency of the electric
impulses, whether telegraphic, telephonic, or other, which are to be transmitted.
The electrostatic capacity distributed along the cable or line is thus balanced
as it were in sections, each organ so introduced into the line or cable exerting
a neutralising effect on the capacity of the cable in the adjacent parts. Thus,
for example, if a self-induction coil, inserted as hereinafter described, is of
sufficient size and power to approximately neutralise the effects of electrostatic
capacity of any cable for a distance of five miles on either side from the point
where it is inserted, it will be expedient to treat that cable in sections, each of
ten miles length, similar self-induction coils being inserted every ten miles along
the cable. It is an important point that these coils should be all alike for any
given sample of cable and at approximately equal distances apart, and it must
specially be borne in mind that the compensation to be effective must be local ;
that is, the compensators must be sufficiently mumerous.and distributed throughout
the length of the cables.
Self-induction coils for use as compensators, as also the mutual induction coils
hereafter described, should have not only a high time-constant but a high resistance
relatively to that of the sections of cable which they are to compensate or connect.
In cases where it is important to avoid a material weakening of the transmitted
currents from flow through the compensators, it is preferable that the resistance of
the compensators should be greater than that of the entire cable. The coils should
have each such dimensions and be made with such a number of turns of wire of
such a gauge (wound around a well laminated iron core, of such shape and length)
that the time-constant (or interval of time that is needful for the current in the
said coil to rise to 0.634 of its final value) shall be not less than, and shall be
preferably greater than, o second, whilst the resistance of each coil shall prefer-
ably be greater than that of the ten mile or twenty mile section of the cable, and
shall indeed, in the cases just previously mentioned, be with advantage as great as
or greater than the resistance of the entire length of the conductor. As already
stated, the entire line can be divided up into a series of shorter circuits by mutual
induction devices between each section.
The essence of the sectioning of the cable is that, since retardation results from
there being a capacity distributed along a great length, one should so modify the
system that movements of electricity to effect the charges and discharges of the
accumulations in the cable can take place over short lengths of circuit instead
of having to flow in and out from the ends up to the places where the charge has
accumulated.
In those cases where coils are so employed to produce mutual induction between

page_text: successive sections, the directions already given for self-induction coils apply
equally.
In cases where double induction coils are arranged in the two lines or conductors
(instead of across them) as in Figure 3 hereafter described, the coils, though they
should in general have time-constants and cores (if any) as before, must be of
resistance lower than that of the rest of the circuit, and their windings may with
advantage be interwound, that is to say, not separated into two coils, primary and
secondary, each apart from the other, one inside, the other outside; or one at one
end of the core, the other at the other, but wound between one another so as to
lie as nearly as possible geometrically in identical relations to their core.
In electric cables, the induction coils must be further arranged so as not to form
unwieldy enlargements of the cable, and are preferably long and narrow and with
the axes parallel to that of the cable.
Ordinary electro-magnets with the usual iron cores will not do; iron cores,
when they are employed, must be made of a relatively small amount of very well
laminated iron.
If the above fundamental principle, as to distribution of the compensators, high
resistance in the wire and lamination of any iron used in their construction, be borne
in mind, other ways of obtaining the requisite induction in various parts of a cable
may be employed with success.
I will now describe my invention as applied in practice
:-
I take a multiple conductor composed of two or more insulated metallic wires.
These will, in the case of cables, be usually, if not invariably, included in the same
sheath. I arrange, at suitable distances along them, compensators, the simplest
form of which is diagrammatically shown in Figure 1 of the accompanying drawings,
and consists of a wire of high resistance coiled round a coil of well laminated iron
(preferably composed of numerous fine wires insulated by rust or otherwise from
each other) joining the two wires. The coil is of course (as well as the core)
covered with insulated material and its choking or self-inducing action, if it
consists of a sufficient number of turns of fine wire coiled near together, will cause
sufficient resistance to prevent all but an insignificant quantity of the working
charge to short circuit.
I may, however, adopt one or other of the arrangements shown in Figure 2. In
these, the cable is divided into sections which form complete metallic circuits, the
portions electrically contiguous to the next section forming coils acting on one
another by mutual induction. In the last mentioned cases, it is not necessary, to
have an iron core as is the case in the arrangement shown in Figure 1.
Figure 3 shows an arrangement in which the two lines are wound round each
other with or without a core at intervals to form double induction coils.
Figure 4 shows a modification of the above, in which two wires in the same
cable are at intervals coiled in opposite directions round each other or round a
common core.
Figure 5 is a modification in which the core (which should be constructed as
above described) forms part of one of the conductors, the shunt being coiled round
it. It is advisable, if this construction is used, to make the one wire the core in
each alternate compensator and the other wire the core in the remaining ones.
Figure 6 shows an arrangement of two conductors of which one is continuous and
the other is cut into sections the ends of which overlap sufficiently to admit of
induced currents flowing by mutual induction. Or condensers can be used between
the sections of the conductor, and this arrangement can be combined with induction
coils formed by winding the two conductors round each other with or without a core
so as to form double induction coils.
This invention can also be applied to cables which contain more than two
conductors.
An example is shown in Figure 7, which shows two conductors connected with a
third one by compensators of the above description; and in Figure 8 which shows
three conductors similarly connected to one another. two by two.

page_text: Figures 9 and 10 show modifications, the arrangements in which will be readily
understood from the diagrams.
Figure 11 shows a cable in which three conductors are connected together by
double induction coils;
Figure 12 where two lines are joined by double induction coils and a third
line is coiled in double induction manner round cores placed in each circuit; and,
Figure 13 where four lines are connected in a similar manner to plans already
described in the case of three wires.
In Figure 14 two lines are joined by compensators and a third is connected to
the centre of these compensators by coils of half the length of the other com-
pensators; in this way a star of compensators could be formed uniting several wires
with coils of equal length to one point or wire.
In some cases it may be practicable to use an uninsulated conductor in the place
of one of the wires above referred to, but such an arrangement will usually be
greatly inferior to the twin or multiple conductor system in which all the con-
ductors are insulated. But in all cases it is necessary to bear in mind as an
essential part of the invention that the compensators must be distributed through
the length of the cable so as locally to counteract the effect of the static inductive
capacity of the cable which is itself distributed over the whole length of the cable
and that the completeness of the counteraction will depend upon the compensators
being sufficiently numerous thus locally to destroy the ill effect of the static
induction. In other words, the cable must have compensators at sufficiently short
distances to render it possible to practically multiply, by means of the com-
pensators, the effect of the static induction in the lengths of the cable between the
compensators.
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. A cable containing twin or multiple insulated conductors with compensators
arranged at intervals throughout the cable so as to counteract the effect of static
induction substantially as hereinabove described.
2. In a cable containing twin or multiple insulated conductors (whether in
sections or continuous throughout the length of the cable) the method of counter-
acting the effect of static induction by compensators arranged at intervals throughout
the cable substantially as hereinabove described.
3. The application to lines and cables at intervals throughout their length of
compensators of the kind hereinabove described so as to counteract the effect of
static induction in the manner and substantially as herein set forth.
4. The herein described arrangements for counteracting the effect of static
induction as applied to electric lines and cables.
5. The modifications of the hereindescribed arrangements for counteracting the
effect of static induction as applied to electric lines or cables according to which
one of the conductors is uninsulated.
ומה..נינו
Candamban 1000
WM. P. THOMPSON & Co.,
Of Liverpool, Manchester, Nottingham, and London, Patent Agents.