IMPROVEMENTS IN RECEIVING OR RECORDING INSTRUMENTS DAD ELECTRIC TELEAPADIO
Year: 1867

page_text: LETTERS PATENT to Sir William Thomson, Knight, of Glasgow College,
Doctor of Laws and Professor of Natural Philosophy in the University
and College of Glasgow, for the Invention of "IMPROVEMENTS IN RECEIVING
OR RECORDING INSTRUMENTS DAD ELECTRIC TELEAPADIO"
PROVISIONAL SPECIFICATION left by the said Sir William Thomson at
the Office of the Commissioners of Patents, with his Petition, on the
23rd July 1867.
I, Sir WILLIAM THOMSON, Knight, of Glasgow College, Doctor of Laws
and Professor of Natural Philosophy in the University and College of Glasgow,
do hereby declare the nature of the said Invention for "IMPROVEMENTS IN
RECEIVING OR RECORDING INSTRUMENTS FOR ELECTRIC TELEGRAPHS," to be as
follows:-
This Invention has more especially for its object to produce an instrument
capable of recording by permanent marks such electric signals as have up to
the present time being received by the mirror galvanometer as described in
the Specification of a Patent granted to me on the 20th day of February 1858
(No. 329). The peculiar merit of that instrument is that it continuously

page_text: indicates with approximate exactitude the variations of strength in the received
current; the movement of the spot of light follows every variation in that
current, and these varying strengths being followed by the eye can be inter-
preted under circumstances in which ordinary instruments indicating the mere
presence or absence of a given strength of current would be useless. By
my present improvements I am enabled to construct an instrument which
draws or marks on a strip of paper a curved or broken line giving a graphic
representation of the varying strength of current, or if required of electric
potential at the receiving end of the cable, and gives a permanent record of
every feature of the effect due to the sender's action. The instrument is
available for the system of varying strengths, including of course the simplest
system, viz., of two strengths often called positive and negative or for the
system of long and short signals of which the Morse alphabet is the simplest
type. The difficulty in producing such a recorder as this has been due to the
difficulty of obtaining marks from a very light body in rapid motion without
impeding that motion.
To effect this I, according to my Invention, connect (either by direct
attachment or by a stretched thread or fibre) to the body moved by the
received current a light marking needle or tube, from the end of which ink or
other fluid is spurted upon paper. (The signals which are to be recorded give
rise to motions of the marking end which are parallel to the plane of the paper,
while the paper is drawn along in its own plane and in a direction per-
pendicular to the line of the motions caused by the signals.) I employ for
the marking needle, by preference, a capillary tube or bristle dipping at one
end into a stationary reservoir of ink or other fluid, and I cause the ink or
other fluid to be spirted from or drawn from the opposite end by means of
an electric force, or by means of rapid vibrations maintained in the needle or
in the paper in a direction perpendicular to the plane of the paper; these
vibrations may be maintained mechanically or pneumatically as by the agency
of sound, so that the paper receives ink by a succession of fine contacts
between each of which the tube or bristle is quite free to move. When the
electric method is used the paper is drawn over a metal plate electrified, say,
positively, and the capillary tube is electrified, say, negatively, and a powerful
difference of potential is maintained between the tube and the metal plate
such as would tend to cause a succession of sparks to pass between them, and
which in the circumstances produce a fine stream of ink or a succession of fine
dots spirted from the tube on to the paper, leaving a record of the position of
the tube at each instant and drawing a sensibly continuous line on the paper
without impeding by friction the motion of the tube as directed by the receiving

page_text: instrument. I prefer to let the paper move in a vertical plane and to use a
small glass syphon with its short leg dipping in the ink reservoir and its long
leg pointing obliquely downwards at the paper and close to it. A similaṛ
effect is produced by the alternative methods described. In connection with
the above I use as a receiving instrument a peculiar arrangement in which
the received current passes through a very light coil of a small number of
turns of fine wire; part of this coil is placed in a very powerful magnetic field
produced by permanent magnets or electro-magnets, which act with great
force on the coil when the current passes throught it. The coil is kept stiff
without any complete framework or bobbin by the use of stiff pieces (like
booms in the rigging of a ship) drawn asunder by threads or strong fibres
stretched to fixed points and serving to support the coil while giving it the
requisite freedom to move and the requisite stability. To multiply the power
when required I use two or more light moveable coils each attached to the
marking needle by a connecting fibre or fibres which may be attached to the
marking needle near its axis so as to magnify the motion of the marking end as
compared with that of the receiving coils. The magnification may be pushed
farther if desired by using a multiplying train of two or more needles.
When vibrations of the needle become troublesome, as may be the case when
the Invention is applied to short submarine cables or to land lines, those
vibrations may be checked by vanes dipping in liquid or other frictional
dampers, or a shunt may be applied to the receiving coil so that currents may
be induced by its rapid motion when the consequent electro-magnetic force of
the magnets on the moving coil will damp the vibrations.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Sir William Thomson in the Great Seal Patent Office on
the 23rd January 1868.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, Sir WILLIAM
THOMSON, Knight, of Glasgow College, Doctor of Laws and Professor of
Natural Philosophy in the University and College of Glasgow, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-third day of July, in the year of our Lord One
thousand eight hundred and sixty-seven, in the thirty-first year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
William Thomson, Her special licence that I, the said William Thomson,

page_text: my executors, administrators, and assigns, or such others as I, the said
William Thomson, my executors, administrators, and assigns, should at any
time agree with, and no others, from time to time and at all times thereafter
during the term therein expressed, should and lawfully might make, use,
exercise, and vend, within the United Kingdom of Great Britain and Ireland,
the Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN
RECEIVING OR RECORDING INSTRUMENTS FOR ELECTRIC TELEGRAPHS," upon the
condition (amongst others) that I, the said William Thomson, my executors
or administrators, by an instrument in writing under my; or their, or one of
their hands and seals, should particularly describe and ascertain the nature of
the said Invention, and in what manner the same was to be performed, and
cause the same to be filed in the Great Seal Patent Office within six
calendar months next and immediately after the date of the said Letters
Patent.
NOW KNOW YE, that I, the said William Thomson, do hereby declare
the nature of the said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement thereof, that is to say :-
This Invention has more especially for its object to produce an instrument
capable of recording by permanent marks such electric signals as have up to
the present time been received by the mirror galvanometer as described in the
Specification of a Patent granted to me on the Twentieth day of February
1858 (No. 329). The peculiar merit of that instrument is that it continuously
indicates with approximate exactitude the variations of strength in the received
current, the movement of the spot of light follows every variation in that
current, and these varying strengths being followed by the eye can be inter-
preted under circumstances in which ordinary instruments indicating the mere
presence or absence of a given strength of current would be useless. By my
present improvements I am enabled to construct an instrument which draws or
marks on a strip of paper a curved or broken line giving a graphic repre-
sentation of the varying strength of current, or if required of electric potential
at the receiving end of the cable and gives a permanent record of every feature
of the effect due to the sender's action. The instrument is available for the
system of varying strengths, including of course the simplest system, viz., of
two strengths often called positive and negative, or for the system of long and
short signals, of which the Morse alphabet is the simplest type. The difficulty
in producing such a recorder as this has been due to the difficulty of obtaining
marks from a very light body in rapid motion without impeding that motion.
To effect this I according to my Invention connect (either by direct attachment

page_text: or by a stretched thread or fibre) to the body moved by the received current a
light marking needle or tube, from the end of which ink or other fluid is
spirted upon paper. (The signals which are to be recorded give rise to
motions of the marking end which are parallel to the plane of the paper while
the paper is drawn along in its own plane and in a direction perpendicular to
the line of the motions caused by the signals.) I employ for the marking
needle by preference a capillary tube or a bristle dipping at one end into a
stationary reservoir of ink or other fluid, and I cause the ink or other fluid to
be spirted from or drawn from the opposite end by means of an electric force
or by means of rapid vibrations maintained in the needle or in the paper in a
direction perpendicular to the plane of the paper. These vibrations may bo
maintained mechanically or pneumatically as by the agency of sound, so that
the
paper receives ink by a succession of fine contacts, between each of which
the tube or bristle is quite free to move. When the electric method is used
the paper is drawn over a metal plate electrified say positively, and the
capillary tube is electrified say negatively, and a powerful difference of potential
is maintained between the tube and the metal plate such as would tend to
cause a succession of sparks to pass between them, and which in the circum-
stances produce a fine stream of ink or a succession of fine dots spirted from
the tube on to the paper, leaving a record of the position of the tube at each
instant, and drawing a sensibly continuous line on the paper without impeding
by friction the motion of the tube as directed by the receiving instrument. I
prefer to let the paper move in a vertical plane, and to use a small glass syphon
with its short leg dipping in the ink reservoir and its long leg pointing
obliquely, downwards at the paper and close to it. A similar effect is produced
by the alternative methods described.
In connection with the above I use as a receiving instrument a peculiar
arrangement in which the received current passes through a very light coil of
a small number of turns of fine wire. Part of this coil is placed in a very
powerful magnetic field produced by permanent magnets or electro-magnets
which act with great force on the coil when the current passes through it.
The coil is kept stiff without any complete framework or bobbin by the
use of stiff pieces (like booms in the rigging of a ship) drawn asunder
by threads or strong fibres stretched to fixed points, and serving to support
the coil while giving it the requisite freedom to move and the requisite
stability.
And in order that my said Invention may be most fully understood and
readily carried into effect, I will proceed to describe the Drawings hereunto

page_text: Figure 1 is an elevation and Figure 2 a plan showing the principal parts of
the recording instrument. A permanent compound steel magnet N, S, made
for convenience sake of a large number of straight steel bars with a soft iron
junction piece and soft iron poles is used to produce a very intense magnetic
field in the deep narrow space separating the poles shown in plan at m,
Figure 2. Figure 3 shows an elevation of a very light coil or skein of fino
silk-covered copper wire stretched on a couple of light strutts or booms between
1, in, and o, n. The side m, n, composed solely of the fine wire is formed into
a thin flat cake by being cemented with paraffin. The side l, o, is strengthened
by a strong thread to relieve the copper wire from strain, and the axis of
suspension is placed nearer the strengthened side, as shown in the Drawing.
The coil is suspended by two fine silk fibres 1, p. and m, q, in such a position
that the side m, n, hangs in the intense magnetic field between the poles of
the large permanent magnet, and is free to oscillate in a direction parallel to
the straight bars forming the magnets. The weight w hung from the bottom
of the coil keeps it in shape and adds directing force to the coil, since any
oscillation on the bifilar suspension will slightly lift this weight. The peculiar
construction of the coil reduces the momentum of the moving parts to a
minimum, the form of the side m, n, as a thin flat strip allows the poles of the
permanent magnet to approach very closely to form a very intense magnetic
field, and the depth of the side m, n, exposes a considerable length of the wire
in the coil to the action of the magnetism of the permanent magnets. I have
obtained good results with copper wire weighing about grain per foot, and
with coils containing about twenty turns. The two ends of the wire forming
the coil are twisted round the suspending fibres, one round each, as shown in
Figure 3, and attached to terminals B, B, Figure 2, and the received current
conveying the signals to be recorded is passed through the suspended coil from
these terminals. So long as no current circulates through the coil it will
hang directed solely by the bifilar suspension and unaffected by the presence
of the powerful magnets, but as soon as a current is received through the
side m, n, of the coil it will be impelled out from between the poles or further
in between them in a direction parallel to the straight bars of the magnets;
the direction of the impulse will depend on the direction of the current and
the magnitude of the deflecting force will depend cæteris paribus on the
strength of the received current. The side m, n, of the coil will move back-
wards or forwards, under the effect of the continually varying currents received
through a submarine cable, and owing to the lightness of the coil it will follow

page_text: rapidly varying currents, so that at each moment its position will correspond
to the strength of the current at that instant. To do this the directing force
of the bifilar suspension and weight should be adjusted so that the free
oscillations of the coil when no current is passing are more rapid than the
oscillations intended to be recorded as signals. The adjustment of the natural.
oscillations to the rate of signalling is facilitated by the use of a damper which
will allow the adoption of a smaller directing power, and consequent greater
range of deflection in the marking point. Any of the usual forms of damper
might be used founded on the friction of solids or fluids; thus a vane dipping
in water may be employed; but good results have been obtained by allowing a
small spring to press on the fibre r, m, to damp the vibrations. The receiving
coil follows the received current as readily as the little mirror and magnet in
my reflecting galvanometer, but the same current in my new instrument pro-
duces a much greater available force to move the parts, and I can make use
of this increase of force to allow a recording apparatus to be combined with
the receiving coil in the following manner: A single silk fibre m, r, iş
attached at one end to the coil at the top of the side m, n, and at the other
end to what I call the syphon of the recording instrument shown in detail and
of full size in Figure 4, and lettered t, r, s. The syphon is suspended with
double threads t, u, x, v, at one side and a single thread v, w, at the other side,
so as to be capable of oscillating round a horizontal axis. The directing force
of the double threads is adjusted so that the syphon can follow the movements
of the side m, n, to which it is attached, keeping the single fibre r, m, always
taut. The distance of the point of attachment r from the axis t, w, may be
about the length of the long leg of the syphon, so that any motion of the
side m, n, of the receiving coil may be represented by a tenfold greater motion
at the end of the syphon. I use as a syphon a fine glass tube bent into the
shape shown in Figure 4, which also shows the paper on which the signals are
to be recorded; this paper moves past the end in a direction perpendicular to
that in which the end moves to indicate the signals; the short leg of the syphon
dips into a dish of ink. A brass plate z, y, across which the paper is drawn
in front of the end of the syphon is connected with an electrical machine by
which it is kept highly charged with electricity, whereas the syphon is in con-
nection with the earth and a series of small and rapid discharges of electricity
take place between the syphon and the plate which cause the ink to be spirted
from the syphon on to the paper. The instrument should be so adjusted that
the syphon will oscillate freely in a direction parallel to the plane of the
paper from twice to ten times in the time occupied in the production of every
wave or signal or separate part of a letter. The ordinary electrical machine

page_text: or Ruhmkorff's coils might be used, but I prefer to use my new induction appa-
ratus, which can be conveniently driven by the clockwork used to supply the
recording paper, which may be of ordinary construction; it is clearly shown
at C in Figures 1 and 2.
The following is a description of the induction apparatus:-A wheel of
vulcanite A, A, Figure 5, with a number of pieces of metal a, a¹, a², etc.,
(called carriers for brevity), attached to its rim is kept rotating rapidly round
a fixed axis. The carriers are very lightly touched at opposite ends of a
diameter by two fixed tangent springs. One of these springs B is connected
with the earth, and the other C with an insulated piece of metal D called the
receiver, which is analogous to the "prime conductor" of an ordinary electric
machine. The point of contact b of the earth spring with the carriers is
exposed to the influence of an electrified body E called the inductor. When
this is positively electrified each carrier when leaving the contact with the
earth spring carries away negative electricity, which it gives up through the
receiver spring to the receiver. The receiver and inductor are each placed so
as to surround as nearly as may be the point of contact of the corresponding
spring. In Figure 5 the receiver and inductor are cut through at e and d to
show the carriers and contacts. From this description it will be seen that the
inductor induces a negative charge on all the carriers inside it, and each carrier
in succession gives up this negative charge to the receiver which is connected
with the brass plate, y, Figure 4, from which it passes to the syphon as
described. The inductor E, Figure 5, for the good working of the machine
should be kept electrified to a high and constant potential. This is effected
by an adjunct called the replenisher. The replenisher is similar in shape and
general arrangement to the inductor, but two contact springs are added, as
shown in Figure 6, and the connections are differently arranged. Two of the
springs C, C₁, called receiving springs, are connected to inductors E, and D₁;
and two springs B, B₁, called connecting springs, are joined together by a wire.
The carrier touches the receiver spring when wholly covered by the corre-
sponding inductor; it touches the connecting spring shortly after breaking
contact with the receiver spring, and while still in great part covered by the
inductor.
The action of the arrangement may be described as follows:-Let one
inductor E₁ be in connection with the earth, let the connecting springs with
the wire joining them be insulated, and the other inductor D, electrified
positively and connected with the other inductor E of the induction machine
Figure 5; let the axis and carriers be turned rapidly in the direction shown
by the arrows, each carrier after passing the contact C, and while in contact

page_text: with 6, will receive a negative charge by induction, while contact spring b₁ and
the carrier with which it is in contact will at the same moment receive a positive
charge, these effects being produced by the redistribution of the electricity in
the insulated system composed of two carriers, the connecting springs, and
wires under the influence of induction. Immediately afterwards contact is
broken at 6 and b₁, so that the two carriers retain their positive and negative
charges until connected with the inductors by the springs c and ; then the
negative charge will go to earth through E₁, and the positive charge will leave
the carrier inside D, to distribute itself on the outer surface of D, in accordance
with the well-known laws of induction; the repetition of this action leads to
an indefinite accumulation of positive electricity on D₁, limited only by the
perfection of its insulation preventing the dispersion of the charge by conduction
or by sparks. The charges of positive and negative electricity are indicated
by the signs and on the carriers. When discharged or nearly discharged
an O is written on the carriers.
In the end view Figure 6 the inductor E, is removed to show the wheel and
carriers. When the recording instrument is at work the brass plate and
paper crossing it being highly charged with statical electricity attract the end
of the syphon, and under the influence of this attraction and of a rapid vibration
produced in the end of the syphon and which is due to continual small
electrical discharges, the ink flies in a succession of fine drops from the syphon
to the paper. These drops blend into a continuous line on the paper as it is
drawn regularly forward. This line records the position of the end of the
syphon at each moment as it is moved backwards and forwards across the
paper by the silk fibre r, m, attached to the side m, n, of the receiving coil.
The line drawn on the paper is therefore a continuous curve corresponding to
the motions of the side m, n, of the receiving coil, and therefore to the varying
currents producing the motions and to the signals which those currents indicate.
When no current is received a simple straight line will be drawn along the
paper; short positive and negative signals will draw small ripples on either side
of the zero line.
Figure 7 shows the letters a, b, c, as drawn by the instrument according to
the Steinhiel code. Earth currents will cause the syphon to make long
sweeps from side to side on the paper, causing curves of small curvature, on
which are superimposed the comparatively short curves of the signals.
In fine, the instrument is adapted to record all signals which can be read
on my reflecting galvanometer. A spring or other adjustment may be used
to bring the paper and the syphon into such a relative position that the marks
may be near the centre of the paper, and the sensibility of the new recorder is

page_text: such that the current from a single Daniell's cell passing through a resistance
of 8,000 ohms (equal to the resistance of the whole Atlantic cable) will
produce a perfectly distinct signal, while the resistance of the coil in the
instrument itself need not exceed 20 ohms. To multiply the power when
required I use two or more light moveable coils each attached to the marking
needle by a connecting fibre or fibres, which may be attached to the marking
needle near its axis so as to magnify the motion of the marking end as
compared with that of the receiving coils. The magnification may be pushed
farther if desired by using a multiplying train of two or more needles.
Mechanical vibrations may be maintained in the long leg of the syphon by
sound instead of by electrical discharges; thus the syphon may be attached
by a single fibre to the end of a tuning fork in vibration, the fibre being in a
direction perpendicular to that in which the motions corresponding to the
signals take place does not injuriously impede those motions, but on the
contrary may be used to give or adjust the directing force. Instead of a tuning
fork a spring set in vibration by an indented wheel, or a plate set vibrating
by the air in a pipe, sounding a note as in an organ pipe, might be used to
give the small vibrations which jerk the ink from the end of the syphon to the
paper. The ink drop at the end of the syphon may touch the paper at the
end of each vibration. The necessary vibrations might also be given from the
paper itself, but I have obtained the best results in the manner above described
at length.
The recording mechanism might be attached to the common single needle
instrument, or the receiving coil and magnet might be used as a relay or
single needle instrument, independently of the recording instrument.
In witness whereof, I, the said William Thomson, have hereunto set my
hand and seal, this Eleventh day of January, in the year of our Lord
One thousand eight hundred and sixty-eight.
WILLIAM THOMSON. (L.S.)