An Improved Method of and Apparatus for Electrical signaling, Chiefly Designed for Use in Connection with Submarine Cables.
Year: 1887

page_text: An Improved Method of and Apparatus for Electrical signaling,
Chiefly Designed for Use in Connection with Submarine Cables.
I, HENRY HARRIS LAKE, of the firm of Haseltine, Lake & Co., Patent Agents,
Southampton Buildings, in the County of Middlesex 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:-
This invention relates to methods of and apparatus for signalling through circuits
of high electro static capacity, such as submarine cables.
When a battery is placed in connection with the home end of a long submarine
cable, a sensible time elapses before the effects of the current become evident at the
distant or receiving end upon any of the instruments heretofore employed in signalling.
The electric current, instead of manifesting itself with its full force or effect, simul-
taneously with or immediately after the closing of the circuit, gradually rises in
strength or increases from a minimum to a maximum, although during the entire
interval in which this effect is taking place the full current may be flowing into the
cable at the sending end. A similar but opposite phenomenon is observed when the
sending end of the cable is transferred from the battery to the ground, as is done in
discharging the cable. In this case there is at first a somewhat sudden fall in the
current which becomes more and more gradual so that a rapid succession of alternate
contacts with the battery and with the earth, at the sending end, produces at the
receiving end an undulating or alternately rising and falling although unbroken
current. If in order to produce each signal it were necessary for the current to rise
from a minimum to its maximum and then fall back to its minimum, the speed of
signalling on long cables would be extremely slow. But instruments have been con-
structed which are capable of following and indicating or recording gradual changes
in the electrical condition of the cable, and when these are used it is only necessary
that the current should vary to the extent of a fraction of its maximum, by which

page_text: means a much greater number of impulses may be transmitted or electrical changes
produced and utilized for signalling, in a given time. The speed of signalling through
any given cable, therefore, depends on the one hand upon the sensitiveness of the
signalling instrument to respond to small variations of current, and, consequently upon
the time that must elapse between the closing of the circuit at the sending end and
the response of the instrument at the receiving end, and, on the other hand, upon its
capability of recovering from such action or operation, and thus upon the time that
must clapse between the grounding of the cable and the restoration of the instrument
to a condition in which it is capable of a new movement or operation. The highest
practicable speed of signalling that has heretofore been attained on a long cable, such
as one of those spanning the Atlantic Ocean, is about fifteen to seventeen words in
a minute.
It has been demonstrated, however, that at the instant of closing the circuit on a
long cable, an extremely feeble current appears at the remote end, but heretofore no
means have been known of utilizing this initial and almost infinitesimal current for
any useful or practical purpose whatever.
I have discovered a means of producing intelligible signals by means of this hitherto
unavailable current, or, in other words, of producing at the receiving end of a cable
signals apparently and practically synchronous with the action or operation of a trans-
mitting key or like device, at the sending end, which makes, breaks, or otherwise
abruptly disturbs the electrical condition of the cable. The radical improvement and
great advantages of a system capable of effecting this are made manifest by the con-
sideration that in all systems of working long submarine cables heretofore known the
speed of signalling has been limited by the sensitiveness of the receiving instruments
or, in other words, to the rate at which such instruments are capable of responding to
current changes, while by my invention, in which the receiving instrument responds
seemingly instantly to the closing or opening of the circuit, or to any change in the
polarity of the current, the speed of signalling is limited only by the ability of the
receiving operator, reading by sound, to interpret and record the messages sent.
The system may be practically carried out in several, though equivalent ways. For
example, I provide an earth connection or ground at each of the opposite ends of a
continuous cable. I use a galvanic battery and an ordinary Morso key connected
directly in the line at the sending end, for producing the necessary current effects or
changes in the electrical condition of the cable, while at the receiving end I employ a
receiving instrument possessing certain essential characteristics to which I have given
the generic name of "Pult."
One form of this instrument which I have found to fulfill satisfactorily the required
conditions consists of a polarized or permanently magnetized core, around which is a
coil of insulated wire, together with a plate supported in close proximity to the end of
the core.
This plate is either of thin sheet iron or of some other material to which
an iron armature is attached. The coil is included directly in the cable circuit and
every movement of the key at the sending end that either connects a battery with or
disconnects it from the circuit through the cable causes the said plate to emit a
distinctly audible sound. Using such a receiver in the manner of an ordinary Morse
sounder, preferably in connection with devices for concentrating the sound and con-
veying it to the ear, messages may be received by it in the same manner as is now
done by the relays and sounders of land lines.
This instrument differs from those heretofore used for receiving cable messages in
that a signal, in this case an audible sound, is manifested upon the first disturbance of
the molecular equilibrium of the instrument consequent upon the begining of the
flow of the current through the coil although no other or further sound is apparent
thereafter from the subsequent molecular changes while the current is increasing
gradually to its maximum strength; but another distinctive sound is emitted at the
very instant when the molecular condition of the instrument due to any given rise in
the current begins to be disturbed by the falling off of the current due to the
withdrawal of the battery or the transfer of the sending end of the cable to earth or
both although no further audible sound is produced by the molecular changes which

page_text: take place while the current falls from that point to zero. And so, also, any change
in the polarity of the current would cause the instrument to emit a sound although no
sound would be produced by gradual changes of current strength immediately
following such reversals of polarity. As opposed to this. principle of operation, all
previous instruments have been brought into action, not by the first impulse of the
nascent or the cadent current, but only after their continued subjection to the influence
of a growing or declining current, this being due to the circumstance that the
indications produced by such instruments have been dependent upon an actual
movement of some of their parts in space, which could only be attained when succeeding
increments of current had produced a sufficiently powerful electro-magnetic effect to
overcome tlie inertia of the moving parts of the instruments.
Both the construction of the receiver and the general arrangement of the circuit
may be very much modified without departure from the principle or law of operation
upon which this discovery is based. Without attempting to set forth in detail any of
the numerous equivalents for the particular form of receiver above described, I may
state that any instrumentality or combination of parts that forms an electrical signalling
apparatus capable of emitting one distinctly audible sound, in response to an abrupt
or sudden, as distinguished from a gradual or continuing, change in the electrical
condition of the circuit with which it is connected or used is an equivalent of the form
of receiver which I have selected in illustration of the principle, and this without
regard to the absolute potential of charge, so long as the polarity of the current
remains unchanged, and also without regard to the extent of such abrupt change.
Instead of sending a battery current directly into the cable, an induction coil at the
sending end may be interposed in the cable circuit and induced impulses of current
developed therein. Or an induction coil may be used at each end of the line that at
the sending end having its secondary in the line, and that at the distant end having
its primary in the line and its secondary forming a local circuit containing the receiver,
moreover, condensers may be introduced into the line at either or both ends as for
the purpose of cutting off earth currents, without departing from the spirit of the
invention.
Having thus set forth the general character of the discovery, 1 shall now describe
the same more in detail by reference to the accompanying drawing.
Figures 1, 2, 3 and 4 are diagrams of different forms or modifications of the
system.
Figure 5 is a part sectional view of the receiving instrument.
The transmitting instruments are not shown in detail, as any ordinary form of
Morse key or other circuit controlling device may be used for this purpose.
Referring to Figure 5, A is a magnetized steel core mounted or supported in any
convenient manner, preferably with the capability of longitudinal adjustment. Sur-
rounding the core is a coil B of insulated wire, preferably near one end or pole, and
in face of such pole and in very close proximity thereto is a plate or disc Cof
magnetic material which is supported by a frame D or by any other convenient
means.
The specific construction of this instrument may be greatly varied. I have used
cores of various lengths and diameters, and coils varying very widely in resistance, I
have also used plates of many shapes and sizes and of different material. For example,
I have used a mica disc with a small button of iron attached to its centre; and all of
these various devices give, in different degrees, the same result. As a specific example;
with an artificial line of about 4800 ohms resistance and 800 microfarads capacity, I
have secured the best results by using a steel core of about five inches in length and
three-eighths of an inch in diameter, the pole or end near the plate being somewhat
reduced in size, say about one-fourth of an inch across. The coil surrounding the
core was of comparatively fine wire and of about four ohms resistance, and the plate
or disc of thin sheet iron two to two and a half inches in diameter. From this and
many other experiments I have demonstrated, first, that preferably the end of the
core or magnet should be quite small, that is to say of not greater diameter than one-
half inch and preferably much smaller, amounting to what may be considered a blunt

page_text: point, and second, that the resistance of the coil surrounding the magnet must be very
low as compared with the line, that is to say, of not more than a few olimis resistance.
I have, however, obtained good results with coils whose resistance was as high as
seventy ohms and even higher.
Figures 1, 2, 3 and 4 illustrate the general manner in which this system is
carried out.
In these figures P and P¹ represent the receiving instruments. at opposite ends of
the cable E. At each end of the cable is also a galvanic battery FF1 of about the
same capacity as those now used in signalling. One pole of the battery is grounded
and the other adapted to be connected to line by an ordinary make. and break
*key G G¹.
Switches H H¹, figure 1, are provided at the terminals for grounding the cable
through the receiver or connecting it with the key. Any other ordinary disposition
of these parts is of course possible. In the present case one operator works the
key G to produce Morse or other signals in the receiver P¹ from which the receiving
operator reads the message.
In figure 2 the same devices are shown, but in this case the upward or back
movement of the transmitting key disconnects the sending end of the cable from the
battery and connects it to ground through wire g. This particular form of key or
transmitter I especially prefer for long cables as it enables the cable to discharge both
ends after each signal.
In Figure 3 induction coils K, K' are used. The batteries in this case are in local
circuits L in which are the keys G G₁ and the primaries of the induction coil. The
secondaries of these coils are grounded at one end and switches H H connect the
cable either with the other ends of the secondaries or with the receivers as is clearly
shown.
In Figure 4 another modification is shown, the arrangement is similar to that shown
in Figure 3 except that the receiving instrument in lieu of being connected directly to
the line is in the secondary circuit of an induction coil M whose primary is in the
line. There is thus a double conversion of current. The interruption of the local
circuit at the sending end induces an impulse in the secondary of the induction coil
connected with it, and this impulse in the cable induces a second impulse which
produces the sound in the receiver. The results obtained by the use of the induction
coils thus arranged appear to be fully equal to or even better than those obtained when
one or no coil is employed.
As I have stated above, the sounds produced by the receiver on a long cable are
due to abrupt or sudden changes in the electrical condition of the line and not to the
gradual rise or fall of the current. Hence for each stroke or up and down movement
of a make and break key or of a three point key at the transmitting end, whether it
be made slowly or rapidly, two distinct sounds are emitted, one when the battery is
applied, another when it is detached. So also, when an induction coil is used, a sound
accompanies the making of the primary circuit and another the breaking. One of
these sounds will always be found slightly more distinct or louder than the other, so
that the conditions should always be such that the louder sound precedes the other, as
for example when an induction coil is used, a break and make or back contact key
should be placed in the normally closed local circuit of the primary. This is shown
in Figure 3. The direct reading of Morse signals, technically termed dots and dashes,
is thus made practicable.
Having now particularly described and ascertained the nature of the said invention
and in what manner the same is to be performed, as communicated to me by my
foreign correspondent, I declare that what I claim is :-
First The method of signalling through circuits of high electro-static capacity,
such as submarine cables, which consists in abruptly changing the electrical condition
of the cable circuit, and utilizing the initial effect immediately attendant upon such
changes to produce at the opposite or receiving end of the cable sounds or audible
signals, as set forth.

page_text: Second-The method of receiving telegraphic signals through circuits of high
electro-static capacity, such as submarine cables which consists in utilizing the initial
effects of current changes in the circuit to produce sounds or audible signals, as herein
described.
Third The combination with a circuit of high electro-static capacity, such as an
insulated submarine cable, of a source of electricity, a transmitter consisting of a key
or circuit controller and a receiving instrument substantially as described capable of
audibly responding to abrupt or sudden, as distinguished from gradual, changes in
the electrical condition of the circuit, as herein set forth.
Fourth The combination of a circuit of high electro-static capacity, such as an
insulated submarine cable, of a source of electricity, a transmitter consisting of a key
or circuit controller, and a receiver consisting of a polarized or permanently magnetized
core having a pointed end or pole, as set forth, surrounded by an insulated coil
connected directly or indirectly, with the cable circuit, and a plate of magnetic metal
in proximity to the pointed end of the core, as herein set forth.
Fifth The combination with a circuit of high electro-static capacity, such as an
insulated submarine cable, of a battery or other source of electricity, a transmitter
consisting of a polarized or permanently magnetized core having a pointed end or
pole, as set forth, surrounded by an insulated coil of low resistance, connected with
the cable circuit and a magnetic plate in proximity to the pointed end of the core, as
herein described.
Sixth The combination with a circuit of high electro-static capacity, such as an
insulated submarine cable having an earth connection at each end, of a battery or
current generator included in the circuit formed by said cable, a transmitter for
making and breaking the continuity of the cable circuit or producing therein equivalent
current impulses and a receiver consisting of a permanent magnet surrounded by a
coil of low resistance and a thin sheet iron or equivalent plate in proximity to the pole
of said magnet, as herein set forth.
Seventh The combination with a circuit of high electro-static capacity, such as an
insulated submarine cable, of a battery, a key or circuit controller, one or more
induction coils included in the cable circuit for converting or reproducing the changes
in the battery current and a receiver, substantially as described, capable of audibly
responding to abrupt or sudden, as distinguished from gradual changes in the electrical
condition of the circuit, as herein set forth.
Eighth The combination with an insulated submarine cable, of a source of
electricity, a key capable of two positions, one of which places the sending end of the
cable in connection with the said source of electricity while the other places the same
in direct communication with the earth, and a receiver included in or receiving
electrical impulses from the remote end of the cable circuit and constructed in the
manner herein described, whereby it is capable of audibly responding to abrupt or
sudden, as distinguished from gradual, changes in the electrical condition of the circuit,
as herein set forth.
Total this 10th day of Anril 1887
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London,
Agents for the Applicant.