IMPROVEMENTS IN ELECTRIC SIGNALLING Apparatus
Year: 1875

page_text: LETTERS PATENT to Benjamin Pryor Stockman, of 3, Poets' Corner,
in the City of Westminster, Civil Engineer, for the Invention of
"IMPROVEMENTS IN ELECTRIC SIGNALLING Apparatus.”
Sealed the 29th June 1875, and dated the 22nd January 1875.

page_text: construction of receiving instrument. By means of the instrument
designated commutating key I modify or neutralize the return currents,
which are generated when an electric current is sent through a sub-
marine telegraph cable or other telegraph line, this is effected by sending
currents varying in duration, tension, or quality.
By this Invention I am enabled to use electro-magnetic or other
secondary coils at the receiving end of submarine cables or other
telegraphic lines, the rebound or sudden change of the direction of the
secondary current, which otherwise takes place upon the making or
breaking the primary current being prevented, and thus the deflection of 1
the "receiving instrument" in any direction required is ensured.
My "key" provides also an improved means of putting the end of
the line to earth immediately after each signal and then immediately
insulating it.
The following is a general description of my "key" aided by the 1
accompanying Drawing.
A is a lever of an arched form connected with a radius arm b, the
lever being a true are struck from the centre c and moving upon it.
The radius arm 6 is loaded by a counterbalance weight & which forms the
tail end of the key, and is attached to the lever by a joint e, so that the 2
lever is free to move beyond its true relative position with the centre c
as a circular arc, but the stopf prevents the lever from drooping or
drawing nearer to the centre c than its true position as a circular arc.
The other end of the lever is formed for making contact cither by finger
tappets g, or by separate pistons or plugs pressing upon them, in which 2
latter case the whole may be covered up in a box.
The lever contains a set of pegs h, h, of which there are two shewn in
the Drawing, but there may be three or more. The pegs are capable of
being set or adjusted to various positions and distances apart, or to any
length in the radial direction of the levers, there being slots in the levers 3
provided to allow of their longitudinal adjustment, and the pegs having
screw threads working in nuts can be raised or lowered as required. I is
a roller moving freely on its bearing k; the surface of the roller is at a
lower level than the under side of the lever, allowing a space for the ends
of the pegs which have to press upon the roller; the main centre c and 3
centre of roller kare in one true vertical line; L is a contact point putting
5

page_text: the line to earth which may be raised or lowered to suit the stroke of the
lever; the spring m prevents the lever from dropping so low on the
joint e as to put the, pegs into contact with the-roller until pressed by
the hand of the operator; it also takes the pegs out of contact from
the roller the moment the pressure of the hand is removed, or before the.
lever can fall back (on the centre c) due to the counterbalance weight d.
There arc of course two of these keys forming a pair to transmit the
opposite currents, and the connecting wires from the various parts of the
keys to the terminals are attached in the usual way.
The rollers may be only two in number (one for cach key or set of
pegs), in which case they are cach made in two halves insulated from
each other by ivory, ebonite, or some other suitable non-conducting
material, the battery connections being made perfectly distinct with each
half roller, or there may be separate rollers for cach battery, that is to
say, two or more rollers to cach key. The rollers are made with their
surfaces smooth, rough, or corrugated, or formed with teeth or cams,
and the pegs of the levers are made in cach case to suit the contact
between them and the rollers.
The keys are capable of various adjustment with respect to the battery
line or carth connections, any one of which may be interchanged for
another.
"
The "
receiving instrument is for the purpose of rendering the
currents thus transmitted intelligible at the distant station, and
exhibiting the deflections due to their various changes and successions.
The instrument consists of a very fine wire of platinum, gold, or other
suitable non-magnetic metal suspended at its ends in form of a loop
which hangs pendulous, one end being connected with the line, and the
other to earth. The loop thus formed is placed within the field of a
system of magnets, permanent or electro, so arranged that it is attracted
or repelled by them according to the direction of the passing current.
The sensitiveness of the instrument is proportioned to the power of the
magnets, and is regulated as required by varying its distance from them.
When the signals are very weak as those received through a long cable,
I prefer to use an electro-magnet of sufficient size having a sufficiently
powerful voltaic current circulating in its coils.
To protect the receiving instrument from injury and from currents of
air, the metallic loop is provided with a case of glass or other suitable

page_text: transparent substance, and the whole instrument is enclosed in a
portable and compact case, and I sometimes use a ground glass dial in
front similar to a clock dial, and by means of a bull's cye light or magic
lantern which may also be enclosed with the instrument, I throw a well
defined image of the pendulous loop of wire upon the ground glass,
through which its deflections can be seen and read most clearly.
I also use the fine wire in other forms besides the loop described, as
for example, I fix it in a single line, the ends being attached top and
bottom.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Benjamin Pryor Stockman in the Great Seal
Patent Office on the 22nd July 1875.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, BENJAMIN
PRYOR STOCKMAN, of 3, Poets' Corner, in the City of Westminster, Civil
Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent bearing date the Twenty-second day of January, in the year of
our Lord One thousand eight hundred and seventy-five, in the thirty-
eighth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Benjamin Pryor Stockman, Her
special license that I, the said Benjamin Pryor Stockman, my exc-
cutors, administrators, and assigns, or such others as I, the said Benjamin
Pryor Stockman, my exccutors, 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 ELECTRIC SIGNALLING APPARATUS," upon the
condition (amongst others) that I, the said Benjamin Pryor Stockman,
my executors or administrators, by an instrument in writing under
my, or their, or one of their hands and scals, 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 Scal Patent Office within six calendar months next and
immediately after the date of the said Letters Patent.

page_text: NOW KNOW YE, that I, the said Benjamin Pryor Sockman, 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 :-
1
This Invention has for its object the transmission of electric currents
through submarine cables or other telegraphic lines with more precision,
distinctness, and rapidity than heretofore.
"
One part of the Invention is a new "key" which I call a commu-
tating key," and the other is a new "receiving instrument," and when
these instruments are working in combination they are at opposite ends
of the cable or other telegraph line, the key being at the sending end,
and the receiving instrument at the receiving end. The first of these
instruments, namely, the key, by its use modifies or neutralizes the
return currents which are generated when an electric current is sent
through a submarine telegraph cable or other telegraph line, and this is
effected by sending (by the key) currents varying in duration, tension,
or quality, the peculiarity of the key being its property of blending the
currents or overlapping them, so that there need be no interval of time
or space between each successive current.
The key is also the means of using or rendering efficient electro-
magnetic or other secondary or induction coils at the receiving end of
submarine cables or other telegraphic lines, inasmuch as it prevents the
rebound or sudden change of the direction of the secondary current,
which otherwise takes place in induction coils upon the making or
breaking the primary current, and therefore by the use of the key
a secondary current can be used as the deflections of the receiving
instrument can be ensured in any direction by the key.
The key also provides an improved means of putting the end of the
line to earth immediately after each signal, and then immediately
insulating it.
Various views of the key are shewn at Sheet 1 of the Drawings here-
unto annexed.
Figure 1 is a side view of the key with section of enclosing box;
there are two keys placed side by side for the purpose of sending +
and or opposite currents; Figure 2 is a plan view of the pair of keys;
Figure 3 is an end view of the keys, and section of enclosing box;
-

page_text: Figure 4 is a complete end view outside the enclosing box. The letters
of reference apply to all the Figures on the Drawing.
a is a curved lever, being an arc of a circle. This lever has slots in it
at b, b, in which screw pegs c, c, are placed and secured in any required
position by the nuts underneath at d, d. The screw pegs are fitted
radially in the curved lever, and can be raised or lowered and fixed in
any longitudinal position within the limits of the slots b, b. The curved
lever is jointed at e to a tail piece or tumbler which is again jointed
at g by a radius arm h fixed rigidly to the tumbler f, the centre 9 being
the centre from which the arc of the curved lever (a) is struck; k, k,
k, k, are rollers moving freely on their bearings 1; m, m, are two contact
points touched by the curved levers at the completion of their downward
stroke; n, n, are pistons with ivory or other buttons o, o, to be pressed
by the fingers of the operator; p, p, are links or slings to allow of the
vertical and circular motion of the curved levers; q is the standard or
bearing for the radius arm h; r, r, r, r, the standards carrying the
rollers; s is the upright carrying the contact points with wires to earth;
t is a piece of india-rubber or soft material to prevent noise or harsh
contact when the tumbler (f) falls; u, u, are stops for the tumbler to
fall upon, and may be regulated to any height; v, v, v, v, v, v, arc
six terminals to the various wires; w is a spring to keep up the curved
lever; x is a box or casing enclosing the whole of the key.
The key is used as follows:-The curved lever (a), tumbler (ƒ), radius
arm (h), and standard (q) are all connected, and connected with line.
The four rollers (k, k, k, k,) are perfectly insulated from each other, each
being connected to a separate battery or portion of battery. The contact
points (m, m,) are connected to earth; the various wires from each are
carried to their respective terminals (v, v, v, v, v, v,) in the usual way.
The whole of the parts are of metal except where insulation is
required, when vulcanite or other non-conducting material is used.
The screw pegs (c, c,) are set one in arrear of the other in the slots
(b, b,) on the curved key, and by pressing the button o the spring (w)
yields, and the curved lever first turning on the joint (e) brings the
advanced screw peg in contact with one of a pair of rollers (k), when
a current passes from the roller through the curved lever to line, and
this current continues so long as that screw peg keeps in contact, the
duration of the contact depending upon the radial length of the screw

page_text: peg and its position in its slot b. The finger still pressing the button o
the screw peg turns the roller round, and as the curved lever advances
on the centre g the second screw peg comes in contact with the other
roller of the pair, and another additional current then runs from that
roller through the curved lever, following the first current just before
it is cut off, or before the first screw peg has traversed out of contact
from the first roller, and after sufficient duration of contact with the
second screw peg, the end of the curved lever comes in contact with
the contact point m, and the current is to earth; then by taking off
the pressure from the button o the spring w throws up the curved
lever on the joint e and the line wire is insulated. This action, if
properly arranged, prevents the recoil or rebound in the induction coil
at the further or receiving end of the line, which would otherwise
take place by the cutting-off of the first primary current.
The second screw peg may be made either to put on a current of
opposite electricity, or of the same as the first, but of different intensity
or quantity, as may be found most suitable.
-
It will be understood that the pair of keys are for the purpose of
alternating the currents to cause the right and left hand deflections of
currents.
the receiving instrument, one key sending + the other
The keys may have more than two rollers each, and more than two
screw pegs.
of
The second Invention or "receiving instrument" is for the
purpose
receiving the currents and exhibiting deflections due to their succession
and changes. It comprises the use of a very fine wire, which is sus-
pended pendulously from an upper support at both its ends as a loop or
similar to the letter U, its line and earth terminals being both at the top,
but a single wire may be used with a top and bottom termination. The
wire is enclosed in a glass case or other transparent protection to prevent
derangement from the action of dust or damp. On each side of the wire
is a magnet (either a permanent or electro-magnet, according to the
strength required).
The magnets are separate and independent, so that the two poles
presented are alike; but sometimes one single bar magnet is used, in
which case the pole is inserted in the loop of the wire and not outside.
In either case an attraction of the one side of the wire loop and
repulsion of the other takes place at the same time. Should, however,

page_text: a single wire be used it would require to be encompassed by the two
opposite poles, or by a horse-shoe magnet.
The wire may be rolled or flattened. The current at the receiving end
passes into the wire at the line terminal and escapes at the other
terminal to earth; but while charged by the current the wire deflects to
one side or other, as required, by the attraction and repulsion of the
magnet or magnets, while a dark lantern or magic lantern attached to
the apparatus magnifies a portion of one of the wires by throwing its
image on to a ground glass screen, or if more convenient on to an
opaque screen.
The Drawing of receiving instrument illustrates the description more
in detail.
Figure 1 is a side section shewing the wire in its glass case, a pair of
electro-magnets, the lantern, and the screen of ground glass; Figure 2
is a sectional plan shewing the same; Figure 3 is an end view shewing
the looped wire, but has the lantern removed; Figure 4 is an end view
or outside view of the ground glass screen with the magnified image of
the wire upon it. The letters of reference are the same for all
Figures.
a, a, is the wire loop; b, b, connecting wires to terminals; c, c, ter-
minals to which also are attached the wires to line or induction coil and
to earth respectively; d, d, clectro-magnets; e, the glass caso enclosing
wire; f, a small opening or diaphragm forming a field in which a
portion of one wire is situated as the image to be magnified; g, the
magic lantern with usual reflector and lens; h, the ground glass screen
upon which the wire is shewn; k, the magnified image of the wire.
The receiving instrument is drawn to a scale of 3 inches to the foot,
that is to say, for one size of the instrument.
The mode of working the receiving instrument is as follows:-The
line wire or wire from the induction coil, if such is used, is connected
with either of the terminals c, c, and the wire to earth is connected to
the other terminal c. The primary current from the sending end arrives
at the receiving end, passing through the induction coil to earth, but
causing a secondary current through the induction coil, which passes
through the looped wire a, a, to earth, the wire a, a, while the current
passes through it, is attracted to one side by one pole of the magnet,
being aided in its motion by the repulsion of the other pole, and these

page_text: oscillations are indicated on the ground glass or other screen by the
magnified image of the wire. The reverse current charges the wire
with opposite electricity, and the deflections are in an opposite direction,
and thus the signals are formed and read.
Having thus described the nature of my Invention and the manner of
performing the same, I would have it understood, that I claim,-
First. The combined arrangement of commutating key, substantially
as herein-before described.
Second. The combined arrangement of receiving instrument, substan-
tially as herein-before described.
Third. The employment of a loop of wire in the receiving instruments
of electric telegraphs, substantially as herein-before described.
In witness whercof,. I, the said Benjamin Pryor Stockman, havo
hereunto set my hand and seal, this Twenty-second day of
July, in the year of our Lord One thousand cight hundred and
seventy-five.