Improved Means of and Apparatus for the Transmission of Telegraphic Signals.
Year: 1891

page_text: Date of Application, 23rd May, 1891
Complete Specification Left, 22nd Mar., 1892-Accepted, 14th May, 1892
PROVISIONAL SPECIFICATION.
Improved Means of and Apparatus for the Transmission of
Telegraphic Signals.
We, SYDNEY EVERSHED of Kenley in the County of Surrey, Electrical
Engineer, and ALBERT EDWIN GEORGE RICHARDS of 6 Bushey Hill Road,
Camberwell, Naval Constructor, Royal Corps, Naval Constructors, do hereby
declare the nature of our invention to be as follows:-
-
Our invention relates to improved means of and apparatus for the transmission of
telegraphic signals, and is especially applicable to that class of telegraphy in which
a limited number of signals of a specific description are transmitted by electrical
means from one position to another as on board ship. In electric telegraphs
heretofore used for this purpose the signals are transmitted by a series of currents
of short duration which serve to actuate incchanism in the receiving instrument
(herein called the indicator). The signal given by the indicator then depends on
the number of current impulses it has received. If from any cause the transmitting
apparatus (herein called the transmitter) fails to send the requisite number of
currents for any desired signal, or the mechanism of the indicator fails to respond
to one or more of the currents received, the indicator ceases to give signals corre-
sponding with those of the transmitter.
The object of our invention is to make the correspondence between the transmitter
and indicator depend, not on mechanical perfection of delicate parts but on a simple
and direct connection between the relative strength of the signalling currents and
the position of the index of the indicator.
According to our invention the indicator may consist of two coils placed with
their magnetic axes at a suitable angle in the same plane so that the currents in the
coils produce a resultant magnetic field the direction of which depends solely on
their ratio. A permanent or electro-magnet placed in this magnetic field and
pivotted so as to be free to turn until its magnetic axis lies in the direction of the
field due to the coils may be used to indicate the direction of the field and con-
sequently the ratio of the currents in the coils by means of an index moving over a
dial or otherwise. The index may be either fixed on the same spindle as the
magnet or if an expanded angular range is desired without the necessity of a large
range for the magnet, the magnet and index may be fixed to separate spindles
connected by suitable gearing or other mechanism. Any suitable apparatus for
varying the ratio of the currents in the coils, as by varying the resistance in their
circuits or otherwise will serve as the transmitter. Thus a number of resistances
may be used in series, one end of the series being connected by a line wire with one
of the indicator coils, the other end of the series being similarly connected with the
other indicator coil; the two remaining terminals of the coils being both connected
to a common-return wire in which is included a battery or other source of electrical
energy. The circuit is completed through a multiple point switch which serves to
connect the circuit returning through the battery to any point in the series of
resistances. When so arranged the apparatus works as follows:-Suppose the
switch is placed on the middle contact, the battery current will then divide equally
and producing equal fields within the coils the index of the indicator will point to
the centre of its range; moving the switch towards either end of the series of
resistances, removes resistance from one coil circuit and adds it to the other thus
increasing the current in one coil and decreasing it in the other, and consequently
altering the ratio of their magnetic fields and hence the direction of their resultant
field; the magnet and index will now move into a new position. It will be seen
that for each position of the switch there corresponds one, and only one, position of

page_text: the index of the indicator so that by marking the several positions of the multiple
switch and the corresponding positions of the index with the same signals the
apparatus will serve as a telegraph.
When the indicator coil currents are only varied in strength the maximum
angular range of the magnet will be equal to the angle between the magnetic axes
of the coils, but by changing the direction as well as the strength of the coil
currents, or reversing the polarity of the magnet, the latter may be made to take
up any position whatever throughout the whole are of 360°. The same result may
be obtained by the use of more than two coils but only by increasing the number of
line wires.
In some cases the indicator coils may be replaced by electromagnets arranged to
produce magnetic fields at a suitable angle; or the indicator coils may be attached
to the spindle and free to rotate in the magnetic field of a fixed permanent or
electromagnet.
When an indicator is only required to show that an order transmitted has been
obeyed, for example when steering orders are transmitted from the bridge or other
position on a ship to the wheel we may prefer to use a modification of our invention.
Thus the indicator may be made in the form of a detector galvanometer and used
to show the equality of two variable resistances one of which may be varied by a
hand switch operated by the person who gives the order, the other being varied by
a switch mechanically connected to the tiller. The resistances may be electrically
connected by suitable line wires so as to form the two variable branches of a
Wheatstone bridge, other two constant resistances being arranged to complete the
parallelogram of resistances. The indicator at the helm will then be connected as
the bridge galvanometer. The needle of the indicator remains at zero so long as
the two switches are on corresponding contacts, but when an order is transmitted
by moving the hand switch to any desired signal the indicator at the helm will
deflect and the helmsman must put the helm over until the tiller head by moving
the automatic switch restores the electrical balance in the four resistances and
brings the indicator needle to zero again. Instead of making use of the Wheatstone
bridge principle we may wind the indicator as a differential galvanometer, one coil
of which will be in circuit with the variable resistance controlled by the hand
switch the other coil being in circuit with the resistance which is automatically
regulated by the tiller. A detector galvanometer connected in series with that at
the helm may be used as an indicator near the hand switch so that the person
giving the steering orders may see that they have been obeyed.
Since the indications of a telegraph made according to our invention depend
solely on the ratio of currents or resistances the constancy of current or E.M.F. is
of very little importance. Where ships are electrically lighted current for working
the telegraph apparatus may be taken from the lighting mains, either directly, or
through the medium of secondary cells.
Our invention is applicable to engine room, gun training, and steering signalling
on board ship and in general for any purpose provided the whole number of
different signals to be transmitted can be conveniently shown on a dial.
Dated this 23rd day of May 1891.
FELL & WILDING,
1, Queen Victoria Street, London, E.C., Agents for the Applicants.
COMPLETE SPECIFICATION.
Improved Means of and Apparatus for the Transmission of
Telegraphic Signals.
We, SYDNEY EVERSHED, of Kenley, in the County of Surrey, Electrical
Engineer, and ALBERT EDWIN GEORGE RICHARDS of 6 Bushey Hill Road,
Camberwell, Naval Constructor, Royal Corps, Naval Constructors, do hereby
declare the nature of our invention and in what manner the same is to be

page_text: performed to be particularly described and ascertained in and by the following
statement:-
Our invention relates to improved means of and apparatus for the transmission
of telegraphic signals, and is especially applicable to that class of telegraphy, in
which a limited number of signals of a specific description are transmitted by
electrical means from one position to another as on board ship. In electric
telegraphs heretofore used for this purpose the signals are transmitted by a series
of currents of short duration, which serve to actuate mechanism in the receiving
instrument (herein called the indicator). The signal given by the indicator then
depends on the number of current impulses it has received. If from any cause
the transmitting apparatus (herein called the transmitter) fails to send the requisite
number of currents for any desired signal, or the mechanism of the indicator fails
to respond to one or more of the currents received, the indicator ceases to give
signals corresponding with those of the transmitter.
The object of our invention is to make the correspondence between the trans-
mitter and indicator depend, not on mechanical perfection of delicate parts, but on
a simple and direct,connection between the relative strength of the signalling
currents, and the position of the index of the indicator.
According to our invention the indicator may consist of two coils, placed with
their magnetic axes at a suitable angle in the same plane so that the currents in
the coils produce a resultant magnetic field, the direction of which depends solely
on their ratio. A permanent or electro-magnet placed in this magnetic field, and
pivotted so as to be free to turn until its magnetic axis lies in the direction of the
field due to the coils, may be used to indicate the direction of the field, and conse-
quently the ratio of the currents in the coils by means of an index moving over a
dial or otherwise. The index may be either fixed on the same spindle as the
magnet, or if an expanded angular range is desired without the necessity of a large
range for the magnet, the magnet and index may be fixed to separate spindles
connected by suitable gearing or other mechanism. Any suitable apparatus for
varying the ratio of the currents in the coils, as by varying the resistance in
their circuits or otherwise, will serve as the transmitter. Thus a number of
resistances may be used in series, one end of the series being connected by a line
wire with one of the indicator coils, the other end of the series being similarly
connected with the other indicator coil; the two remaining terminals of the coils
being both connected to a common return wire in which is included a battery or
other source of electrical energy. The circuit is completed through a multiple
point switch, which serves to connect the circuit, returning through the battery to
any point in the series of resistances. When so arranged the apparatus works as
follows:-Suppose the switch is placed on the middle contact, the battery current
will then divide equally, and producing equal fields within the coils, the index of
the indicator will point to the centre of its range; moving the switch towards
either end of the series of resistances, removes resistance from one coil circuit and
adds it to the other, thus increasing the current in one coil and decreasing it in the
other, and consequently altering the ratio of their magnetic fields, and hence the
direction of their resultant field; the magnet and index will now move into a new
position.
It will be seen that for each position of the switch there corresponds one, and
only one, position of the index of the indicator, so that by marking the several
positions of the multiple switch and the corresponding positions of the index, with
the same signals, the apparatus will serve as a telegraph.
When the indicator coil currents are only varied in strength, the maximum
angular range of the magnet will be equal to the angle between the magnetic axes
of the coils, but by changing the direction, as well as the strength of the coil
currents, or reversing the polarity of the magnet, the latter may be made to take
up any position whatever throughout the whole arc of 360°. The same result may
be obtained by the use of more than two coils, but only by increasing the number
of line wires.

page_text: In some cases the indicator coils may be replaced by electro magnets, arranged
to produce magnetic fields at a suitable angle; or the indicator coils may be
attached to the spindle and free to rotate in the magnetic field of a fixed permanent
or electro magnet.
.
When an indicator is only required to show that an order transmitted has been
obeyed, for example when steering orders are transmitted from the bridge or
other position on a ship to the wheel, we may prefer to use a modification of our
invention. Thus the indicator may be made in the form of a detector galvanometer
and used to show the equality of two variable resistances, one of which may be
varied by a hand switch, operated by the person who gives the order, the other
being varied by a switch mechanically connected to the tiller. The resistances
may be electrically connected by suitable line wires so as to form the two variable
branches of a Wheatstone bridge, other two constant resistances being arranged to
complete the parallelogram of resistances. The indicator at the helm will then be
connected as the bridge galvanometer. The needle of the indicator remains at
zero so long as the two switches are on corresponding contacts, but when an order
is transmitted by moving the hand switch to any desired signal, the indicator at
the helm will deflect, and the helmsman must put the helm over until the tiller
head by moving the automatic switch restores the electrical balance in the four
resistances and brings the indicator needle to zero again. Instead of making use
of the Wheatstone bridge principle, we may wind the indicator as a differential
galvanometer, one coil of which will be in circuit with the variable resistance
controlled by the hand switch, the other coil being in circuit with the resistance
which is automatically regulated by the tiller. A detector galvanometer, connected
in series with that at the helm, may be used as an indicator near the hand
switch so that the person giving the steering orders may see that they have been
obeyed.
Since the indications of a telegraph, made according to our invention, depend
solely on the ratio of currents or resistances, the constancy of current or E.M.F. is
of very little importance.
In order that our invention may be the better understood we will now proceed
to describe the same in relation to drawings hereunto annexed, reference being had
to the letters and figures marked thereon. Like letters refer to like parts in the
various figures.
Figure 1 is a view of apparatus with connections adapted to move the active
indicating part through a small angle ciz. anything under 90°.
Figure 2 shows the apparatus adapted to indicate through 360°.
Figure 3 is a view showing the magnetic part fixed, and the coils movable
in contradistinction to the instrument shown in Figures 1 and 2.
Figure 4 is a modified form of instrument in which the turning moment on the
movable system has been much increased.
Figures 5 and 6 are diagrammatic views of arrangements of circuits and
instruments.
The apparatus shown in Figure 1 comprises the essential parts of a telegraph,
made according to our invention, which is constructed as follows:-Surrounding a
pivotted soft iron needle F F (capable of rotation about the axis O in the plane of
the paper) are two pairs of coils A and B, having their magnetic axes passing
through O, at right angles or any other convenient angle. The coils A and B are
each made in two halves, in order to allow the axle to pass through and project outside
the coils in order that an index I may be attached and made to move over a scale
on a dial.
In this Specification the phrase "ratio coils" means two coils having
their magnetic axes in one plane and crossing each other at an angle. They may
be fixed or movable. The axes may be at any angle; a right angle is generally
convenient.
These ratio coils A and B with needle, index, and dial complete, are herein
called the indicator.
One terminal of A is connected through the line wire L' to one end of a

page_text: resistance R; the corresponding terminal of B being connected to the other end
of R, while the two remaining terminals of A and B are connected to a common
return L, which, after passing through the battery E or other source of E.M.F.,
is connected to the central pirot of a multiple point switch S.
The switch S serves to make contact at any one of several points in the resist-
ance R, and thus regulates the relative strength of the currents in A and B.
The operation of this telegraph is as follows:-Assuming that A and B produce
equal magnetic fields for equal currents in their windings, and that the resistance
of A+ L is equal to B +L' the needle F F will lie at 45° with the axis of A on
one side and B on the other, when the switch S is on the middle point of R ; since
in this position the current from E divides equally between A and B.
Moving S to the left will now increase the current in A, and diminish that in B,
and consequently the direction of the resultant field of A and B will shift towards
the axis of A carrying with it the needle FF. This motion will be indicated on
the dial by the index I. Similarly a movement of S to the right, will move F F
in the other direction and I will move to the right.
Hence for each contact on S there corresponds one definite position of the index I
and if each contact has a certain signal marked against it, and the corresponding
positions of the index I are similarly marked, the signals made by moving S will
be reproduced on the dial of the indicator by the index I.
It will be noticed that the indicator shown in Figure 1 only allows the index to
move through a maximum angular range equal to the angle between the magnetic
axes of the ratio coils A and B, and the whole of this range can only be used by
arranging the switch S to break the circuit of one of the coils and so allow the
needle FF to lie exactly along the axis of the other coil. We prefer to allow a
shorter range only so that there is no occasion to break the circuit at any point in
the range of the switch. It is frequently of great importance that the signals on
the dial should be widely separated; and if a longer angular range is required to
meet this condition, the index and needle are placed on separate axles connected
by gearing so that a small angular movement of the needle may produce a large
annular movement of 1.
A hardened steel needle permanently magnetised, may be used in place of the
soft iron needle FF, provided it is not subjected to de-magnetising forces, such as
would be caused by the accidental reversal of the current in the ratio coils A
and B. When the indicator is fixed in a position, free from vibration and extraneous
magnetic forces, and worked by a battery current we prefer to use a permanently
magnetised needle in order to secure some additional turning moment round
the axle.
When a permanently magnetised needle is employed, the index may be made to
take up any position throughout the whole 360° of the dial without the use of
gearing. Figure 2 shows an indicator and transmitter arranged to secure this
result. A and B as in Figure 1 are two ratio coils with their axes at right angles;
NS being a permanently magnetised needle. The transmitter consists of two
resistances R and R2 having their middle points connected to a battery E or other
source of E.M.F. Four contact arms aa bb are fixed to a common axle, and are
insulated from one another and from the axle. The arms aa are connected by
means of brushes pressing on insulated rings to the line wires L' L³, which at their
farther ends are connected to the terminals of the A coil. The switch arms bb
are in a similar way connected to the B coil. These four arms are arranged at
right angles and their ends play over a series of contacts in connection with the
resistances R' R².
With the switch in the position as shown in Figure 2, the coil A having no
resistance inserted by the switch is traversed by the maximum current while the
arms not being on any of the contacts the current in B is zero; the needle
therefore lies along the axis of A. If the switch axle is moved one step forward
in a clockwise direction, makes contact with one end of RR, thus allowing a
small current to traverse B; at the same time u a will have moved so as to insert

page_text: a portion of R R in the circuit of A, thus reducing its current. NS will now be
deflected in the same direction as the switch axle, a little towards the axis of B.
Moving the switch backwards, in a direction contrary to the hands of a clock,
from the position shown in the figure, would have produced a similar result with
the exception that the current introduced into B by the movement of the arms bb
would have been in the opposite direction and consequently N S would have moved
backwards towards the axis of B. When the switch arms have been moved
through 45° the currents in A. and B will be equal and N. S. will have moved 45°,
and when a a and b have completed 90° rotation the current in A will be zero
and that in B a maximum, so that NS will have rotated 90° also; by adjusting
the values of the portions of R' and R' included between successive contacts the
angular movement of the switch axle and arms will be repeated exactly both in
direction and amount by the needle NS and index I.
The number of separate signals which can be telegraphed by the arrangement
shown in Figures 1 and 2 depends on the number of contacts in the switch: if the
switch arms break connection with one contact before making connection with the
next the number of signals is equal to the number of contacts. If however
the switch arms are sufficiently wide to cover two contacts at once the number of
distinct signals shown by the indicator will be double the number of contacts, for
when the arm or arms bridge two contacts the ratio of the currents in A and B
will be about half way between the value of the ratio when the arm is wholly on
one contact or the other. In other words, the index will have definite positions
about half way between those corresponding to each pair of contacts, and it will
stand in one of these half way positions whenever the arms bridge two contacts.
Instead of using fixed coils and a movable needle or magnet, the magnet may be
fixed and the coils arranged to move in its field. An indicator on this principle is
shown in Figure 3 where P P are the poles of an electro magnet excited by the
coil M. Two ratio coils shown in section at A, B, are wound with their magnetic
axes at right angles to each other and to the axis O on which they are free to
rotate.
Currents from a switch, as shown in Figure 1, being passed through A. and B
Figure III by means of flexible connections or brushes, each coil experiences a
force tending to rotate it until its magnetic axis lies along that of the poles PP
and assuming A and B to inclose equal areas and consist of an equal number of
turns of wire, they will take up the position shown in Figure 3 when equal currents
traverse them.
The index may be either attached directly or through gearing to the axle O.
The electro magnet may either be excited by a wholly independent circuit or
preferably by including the coil M in the common return circuit of the coils A B,
for although the ratio of the currents in A and B is altered by the movements of
the switch, the sum of the two currents remains practically constant.
When it is not convenient to use an electro inagnet we may substitute a per-
manent magnet in the indicator shown in Figure 3.
The advantage of the arrangement of fixed magnet and movable coils shown in
Figure 3, is that much greater forces can be exerted on the movable system than
in the case of the simple forms of indicator shown in Figures 1 and 2 for the
same expenditure of power.
A method of obtaining greatly increased forces on the movable system of an
indicator, while still keeping the ratio coils A and B fixed, is shown in section and
in plan in Figure 4, where the soft iron needle N N is fixed to an iron axle O
which is pivoted in deep holes in two soft iron cores of large ironclad electro
magnets MM². The two ends of the needle thus become poles of the same sign
either both north or both south, while the edges of the iron tubes covering the
coils M M² form the opposite poles, either south or north. By this method of
magnetising a needle of enormous moment compared with its weight may be easily
made, while the external or stray field of the magnetic system is very small,
frequently a point of much importance on board ship.

page_text: Each pole of the needle is free to move within a pair of ratio coils A B having
their magnetic axes at right angles. The angular movement of N' N is reproduced
on a dial by means of an index fixed to an axle which is geared to the axle to
which N N is attached. The method of working this indicator is precisely the
same as that described with reference to Figure 1. As in the case of the magnet
in Figure 3, the electro magnets in Figure 4 may be very conveniently excited by
including the coils M M² in the common return circuit of the telegraph.
In Figure 5 we give a diagram of the connections for a complete ships steering
telegraph, which may be taken as an example of the application of our invention in
cases where the position of some apparatus is to be indicated at a distance.
In
T¹ is a transmitter, consisting of resistance R and movable contact S', which is
geared direct to the tiller head of the rudder. is connected to an indicator I¹
placed in the steering compartment of the ship and in addition to the indicator 13,
which is placed on the bridge or other position from which the ship is worked.
these indicators A B and A³ B³ represent the ratio coils while M M³ represent
the field magnet or exciting coils shown in Figures 3 and 4.
After passing
through M³ the circuit is led to the movable contact S2 of the transmitter T which
must be placed close to the indicator 13 and may be conveniently included in the
same case with it. T, serves to transmit signals to the indicator I, placed in the
steering compartment. M. being the exciting magnet belonging to I.
As the A and B circuits do not unite after passing through I,, it is necessary to
excite M₁, by means of a branch circuit from the common return wire between T₁
and 12. This is easily arranged as I and I, will usually be placed side by side.
The source of E.M.F. may be introduced in any part of the common return
between T, and I,, or where shown, in the common wire between 1, and T.
The operation of the telegraph shown in Figure 5 is as follows-When the
officer working the ship desires the rudder to be moved to any position, he moves
the switch handle of the transmitter T, to the corresponding point and this signal
being shown on the dial of indicator I, the steering engine-man moves the tiller
over until the tiller head by moving the contact arm S of T, to the proper point,
shows on the dial of indicator 1, that the rudder has been moved to the angle
ordered by the officer, and shown on I
The indicator I, repeats the indications of I, and serves to show the officer the
position of the tiller and whether his order has been obeyed.
The indicators described in connection with Figures 1, 2, 3, 4 and 5 give a con-
tinuous indication of the position of the switch arm of the transmitter. Where the
telegraph is merely required to send a signal without giving a continuous indication
of it, we prefer to adopt a simpler method of signalling, shown in Figure 6,
where R and R, are resistances-preferably equal in value-permanently con-
nected to a source of E.M.F., E. Small additional resistances ₁₂ are inserted
at the ends of R, to balance the resistances of the line wires L, L, and so make
the currents in R₁ and R, equal. The switch arms S₁ S, are connected through
galvanometers, G and G₁, serving as indicators by means of a third line wire L.
The electrical principle used is that known as the Wheatstone bridge. If used
as a steering telegraph, S, is connected to the tiller head of the rudder and G₂
is placed in the steering compartment, while T, and G, are placed together on the
bridge or other position from which the ship is worked. The switch contacts of T,
and T, are made to correspond with each other so as to indicate the various angles
at which the rudder may be required to stand, and so long as S, and S, are on
corresponding contacts, no current will flow along L, and consequently G, and G₂
will both stand at zero. When the officer working the ship requires the rudder
moved to another angle, he places S, on the point marked with that angle, and so
disturbs the electrical balance in the circuits, and G₁ and G, are deflected. The
steersman then moves the helm until the tiller head having moved S₂ to the corre-
sponding point with that at which S, stands, brings G, back to zero. The officer
at the same time sees from the index of G₁ moving back to zero that his order
has been obeyed.

page_text: G, and G, may be any reliable form of galvanometer, having permanently
magnetized needles, but we prefer to use the type of galvanometer in which a light
movable coil is fixed on an axis, so as to be free to rotate in the magnetic field of
a powerful permanent or electromagnet.
The telegraphs herein described may be worked either by a battery or by a
dynamo, and where constant-service electric supply mains are available they may
be used as the source of electric energy.
For example, where ships are electrically lighted, current for working the
telegraph apparatus may be taken from the lighting mains, either directly or
through the medium of secondary cells, transformers, etc.
Our invention is applicable to the engine room, gun training, and steering,
signalling on board ship and in general for any purpose, provided the whole number
of different signals to be transmitted can be conveniently shown on a dial.
Having now particularly described and ascertained the nature of this inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is
1st. A system of transmission of telegraphic signals, consisting of means for
altering the ratio of resistances in two circuits as a transmitting instrument, in
combination with means for showing the ratio of the currents in the two circuits as
a receiving instrument; and a source of electrical energy common to the two
circuits.
2nd. In an electric telegraph a transmitter consisting of a device adapted to
vary the resistances of two circuits in combination with an indicator to show the
current ratio in the said circuits consisting of two ratio coils (one coil being in each
of the said circuits) and a magnet the said coils and the magnet being adapted to
act upon one another to effect relative movement.
3rd. In an electric telegraph a transmitter having four contact arms and two
separate sets of resistances, and a source of electric energy in combination with a
receiving instrument, substantially as described and illustrated in Figure 2.
4th. In an automatic telegraph, a transmitter, connected mechanically to the
apparatus the function of which is to be indicated, in combination with one or
more indicators, substantially as described and illustrated in Figure 5.
5th. In such an arrangement of telegraphic apparatus as claimed in Claim 4 two
or more sets of transmitters and indicators coupled in series, and worked by the
same current, substantially as described and illustrated in Figure 5.
6th. The arrangement of apparatus and circuits, substantially as described and
illustrated in relation to Figure 6.
7th. In an indicating device, a movable magnet adapted to be magnetised by
fixed magnets, substantially as described and illustrated in relation to Figure 4.
Dated this 22nd day of March 1892.
FELL & WILDING,
1, Queen Victoria Street, London, E.C., Agents for the Applicants.