Improved Means of Telegraphic Communication with Lightships.
Year: 1892

page_text: Date of Application, 28th May, 1892
Complete Specification Left. 27th Mar., 1893-Accepted, 29th Apr., 1893
PROVISIONAL SPECIFICATION.
Improved Means of Telegraphic Communication with Lightships.
I, SYDNEY EVERSHED of Woodfield Works Harrow Road London W.,
Electrical Engineer do hereby declare the nature of this invention to be as
follows:-
:-
According to this invention telegraphic communication may be carried on
between a lightship and the shore by means of the magnetic induction between a
telegraph-cable laid on the sea bottom in a ring round the ship and passing thence
to the shore and a coil of insulated wire attached to the ship, both the coil and
ring of cable having their magnetic axes in a vertical direction. An alternating
or discontinuous current in the cable or coil will then produce alternate secondary
currents in the coil or cable, and these secondary currents being passed through a
telephonic or other suitable instrument adapted to receive and indicate the presence
of such currents will serve for signalling by means of a code.
The ring of cable must be held in position on the sea bottom by suitable moorings
placed at convenient points round the ring so as to secure it against the dragging
action of any ground swell or shifting of the loose bottom. The area enclosed by
the ring of cable must be determined by the extreme limits of movement of the
ship, for in swinging round her mooring she must not travel outside the cable ring.
The cable may contain either one or a number of insulated conductors the latter
being coupled up at the shore ends so that they are electrically in series and the
ring then forms a coil of as many convolutions as there are conductors. The
outside of the cable should be armoured as in what are known as the "shore-ends"
of telegraph cables.
The coil on the ship may in a similar way be formed by laying an insulated
cable of many conductors round the deck of the ship and connecting the conductors
so that they are electrically in series, or a single insulated wire may be laid in many
convolutions round the ship. In either case the coil so formed must enclose as
large an area as is possible within the limits imposed by the size and shape of the
deck.
The signalling current may be produced by a small dynamo yielding alternate
currents and driven through suitable gearing by a weight or spring or by hand.
Or a battery may be used and the current rapidly interrupted by means of a
revolving contact wheel.
The circuit from the source of current to the cable or coil is made and broken by
a telegraph key by means of which signals of short and long duration may be given
according to the Morse or other suitable code. The receiving instrument may be
a telephone receiver or an electro magnet acting on a reed or tongue of metal tuned
so as to correspond in pitch with the frequency of the secondary currents; the reed
cr tongue will be set in vibration by the alternate attraction and repulsion due to
the secondary currents flowing in the electro magnet.
In cases where it is possible to use a cable-ring and coil each of a large number
of convolutions and the depth of water under the ship is small communication may
be more conveniently carried on by means of suitable telephonic transmitters and
receivers than by the telegraphic instruments described.
A call-bell may be rung by means of a local battery the circuit of which is
closed by a relay adapted to work with the currents in the secondary circuit. A
sensitive relay may be made as follows: a coil in the secondary circuit is made to
set in motion by magnetic attraction and repulsion either a tuning fork or reed or
an oscillating arrangement similar to the balance wheel and hair spring of a watch.
The transmitting instrument is arranged, for the purpose of calling attention, to

page_text: produce currents of a frequency equal to the natural oscillation frequency of the
relay; and the series of properly timed impulses thus given to the oscillating part
of the relay will in a short time produce a large amplitude of oscillation. In order
to close the local bell circuit the oscillating part of the relay is caused to make
contact with a contact screw or stud when the amplitude reaches a sensible amount.
A convenient method of producing properly timed impulses at the transmitting end
is by the use of a large electrically driven tuning fork adapted to make and break
the current in the cable-ring (or coil) and the relay magnet may be made to
operate a similar and equally pitched tuning fork arranged so as to close the local
bell circuit as soon as its amplitude of oscillation reaches a sensible amount.
By these means the cummulative effect of a large number of very small mechanical
impulses is made sufficiently large to effectively close a local circuit. The local
circuit may conveniently be arranged to keep itself closed when once the relay has
made even a momentary contact, so that the bell rings continuously until the
operator's attention has been attracted.
Dated this 26th day of M 1000
SYDNEY EVERSHED.
COMPLETE
SPECIFICATION.
Improved Means of Telegraphic Communication with Lightships.
I, SYDNEY EVERSHED of 1 Woodfield Road Harrow Road London W.
Electrical Engineer 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 :-
According to this invention signals may be made from the shore to a lightship
and vice versa by means of the magnetic induction between a telegraphic cable laid
on the sea bottom in a ring round the ship and passing thence to the shore, and a
coil of insulated wire fixed on the ship; both the coil and the ring of cable having
their magnetic axes in a vertical direction. An alternate or a discontinuous
current in the cable, or coil, will then set up alternate secondary currents in the
coil, or cable, and these secondary currents being passed through a telephone
receiver, or other suitable instrument adapted to receive, and indicate by sound the
presence of, such currents, will serve for signalling by means of a code.
In order to make this Specification of my invention as clear as possible, only so
much of the apparatus as is required for transmitting signals from the shore to the
lightship will be described including the means I adopt for calling attention by
ringing a bell on the ship. The same coil on the lightship and ring of cable on the
sea bottom may be used to signal from the lightship to the shore since their
inductive property is a mutual one; and the instruments for transmitting and
receiving signals from the ship to the shore are merely a duplication of those
herein described.
In this Specification the telegraphic cable laid from the shore on the sea bottom
round the lightship is called for brevity the "cable-ring"; the coil on the ship in
which the secondary currents are set up is called the "secondary coil." Trans-
mitting messages by means of a code-for example the Morse code-is called
"signalling" to distinguish the method from transmission of speech by telephonic
apparatus or "speaking." The whole system of signalling by means of the
magnetic induction of two electric circuits may be, and is herein, called an
"induction telegraph."
A transmitting apparatus, cable-ring, secondary coil and receiving instrument
are shewn in plan in Fig. 1. of the attached drawings; a source of electric energy E
has one pole connected to the contact spring of a rapidly revolving contact wheel W
which serves to send discontinuous currents into the cable-ring A by means of the
signalling key K. The secondary coil B thus receiving rapidly alternating electro-
motive forces, alternate currents are passed through the telephone T and indicate

page_text: their presence by the buzzing of its diaphragm. The contact wheel should be
arranged to interrupt the current several thousand times in a second so that the
note emitted by the telephone may be sufficiently high in pitch. For this reason
I prefer to use a contact wheel in place of the small alternate current dynamo or
magneto mentioned in my Provisional Specification.
Fig. 1 being only a diagram and not drawn to scale shews the cable ring
arranged in a circle having the anchorage of the ship as its centre; but its
actual shape is of very little importance so long as it is laid round and wholly
outside the area over which the ship moves when riding freely on her anchor;
the sole necessary condition being that the ship never travels outside the area
enclosed by the cable-ring.
The cable-ring may either contain one or a number of separate and insulated
conductors. In the latter case the conductors must be connected so that they
form a coil of as many turns as there are conductors. The cable-ring may be
protected by sheathing provided it does not form a conductor electrically con-
tinuous along the cable or increase the self induction by reason of its forming
a short closed magnetic circuit round the cable.
The secondary coil must enclose as large an area as the size of the ship will
allow and should consist of at least 50 turns of insulated wire of as low a resistance
as possible. If the ship is built largely of iron the secondary coil should be
arranged round the outside of the bulwarks and protected by wooden or other
suitable casing. The magnetic axis of the secondary coil must be as nearly as
possible normal to the plane of the ship's decks. A convenient way of making the
secondary coil is to strand together from 50 to 100 insulated wires into a rope
which is then laid one or two times completely round the ship and the two ends
being brought into the telegraph cabin the separate wires are there all connected
in series so as to form a coil of as many turns as possible.
The receiving instrument may be an ordinary telephone, or it may be a telephone
in which the diaphragm is replaced by a light iron strip or reed fixed at one end
only. The reed may be adjusted so that its free vibration period corresponds
approximately with the period of the secondary currents.
The inertia of the reed
must be made very small in order to ensure rapid signalling.
In cases where the ship lies in shallow water and rides on a short anchor chain
the mutual induction between the cable-ring and the secondary coil may be
sufficient to permit communication by telephone transmitters and receivers in place
of code signalling.
As the secondary currents are in all cases too small to ring a bell or actuate any
other device for calling attention, and being alternate currents are unable to work
an ordinary telegraph relay, in addition to the signalling instruments herein
described provide other instruments specially for the purpose of closing a local
circuit in order to call attention. Thus according to my invention alternate
currents or discontinuous currents of uniform frequency are passed through the
cable ring setting up alternate currents of the same frequency in the secondary
coil.
The secondary currents traverse coils and thereby alternately attract and repel
a magnet fixed near the coils. The magnet is arranged to vibrate about a suitable
axis and its free vibration period is adjusted until it exactly equals the period of
the secondary currents. When so adjusted the magnet receives a rapid series of
properly timed impulses causing it to vibrate and the amplitude of the vibrations
gradually increases until the magnet strikes against a suitable contact pin, and so
closes a local circuit and sets a bell ringing. A relay constructed on this principle
may be, and is herein, called a "cumulative-impulse" relay..
The apparatus for calling attention by means of a cumulative impulse relay is
illustrated in Fig. 2. where V G is a tuning fork electrically driven in the well
known manner by means of the coil G and battery E. The interrupted currents
traverse the cable-ring A and the secondary currents in the coil B traversing the

page_text: coil M set the tuning fork V M in vibration and cause it to make a contact at P
which closes the circuit of a local battery E L through an electro-magnet R. The
magnet R attracting its armature Q makes a contact at U closing the local
battery E L through a bell D. This circuit remains closed in consequence of a
spring J being so attached to the armature Q that the latter in moving towards
the electro-magnet R passes through a position of unstable equilibrium so that the
spring maintains firm contact at U when once the electro-magnet R has received a
momentary current. The bell therefore continues ringing until attention has been
attracted.
The two tuning forks V G and V M must be very carefully adjusted to unison
and although shewn in Fig. 2. as similar in dimensions I prefer to use a large
heavy fork for transmission as its frequency is less affected by small variations in
the friction of the contact spring; and a very small and light fork for the cumula-
tive impulse relay so that it may require but little energy to set it in vibration.
In place of tuning forks, vibratory steel reeds or tongues may be used with
advantage for both the transmitter and the relay. A tongue transmitter is
illustrated in Fig. 3 in which the same letters denote corresponding parts to those
in Fig. 2.
A very sensitive relay may be made by replacing the ordinary contact tongue
of a Siemens polarised relay by a vibratory steel tongue and suitably laminating
the cores of the relay so as to adapt it for alternate currents.
Another form of cumulative-impulse relay is shewn in Fig. 4. in which the
vibratory part V takes the form of a small magnet arranged to oscillate about its
centre between the poles N, S of a powerful magnet. A small coil M through
which the secondary currents are passed serves to set the magnet V vibrating
about O, until contact is made at P. This relay is tuned in unison with the
received secondary currents by adjusting the distance between the poles N, S.
The most sensitive form of cumulative-impulse relay which I have been able to
construct is based on the principle of the well known d'Arsonval galvanometer and
is shewn in perspective in Fig. 5. A rectangle of suitable wire V is clamped in
the insulating support I. and adjusted until its free vibration frequency about its
clamped ends is equal to the frequency of the received secondary currents.
The side of the rectangle opposite the support 1, is placed between the
poles N, S of a powerful magnet and the secondary currents being caused to
traverse the rectangle V it receives a series of properly timed impulses and is set
in vibration. In Fig. 5. the fixed contact is shewn carried on a rectangle P exactly
similar in every respect to V and tuned to exact unison with it. The object of
this arrangement is to prevent accidental contact being made when. the relay is
shaken any blow given to the supporting base of the relay causes V and P to
start vibrating at the same instant and in the same phase and they do not therefore
come into contact. The rectangle P may conveniently be connected to a duplicate
secondary coil but in the reverse direction to V so that the secondary currents
set V and P vibrating in opposite phases and bring them into contact. The use of
two vibrators or tongues is not confined to the relay shewn in Fig. 5 but may
conveniently be applied to the other forms of relay described.
The frequency prefer to adopt in working by means of cumulative-impulse relays
is between 20 and 40 complete periods in a second. A relay made as shewn in
Fig. 5 and consisting of a rectangle of copper wire 0013 of an inch in diameter
and 2-4 inches in length, with its short side about 1 inch in length had a frequency
of about 30 periods in a second. A tongue made of watch spring steel about
2 inches longth of an inch wide and 0.006 of an inch thick had the same
frequency when vibrating freely about one end.
At the time of filing my Provisional Specification I was not aware that any
difficulty was found in laying a telegraph cable to a rock lighthouse but my inven-
tion may be used for communication with lighthouses in
cases where it is
impracticable to lay a cable over the rocks into the lighthouse.

page_text: Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
(1) An induction-telegraph comprising a cable-ring laid on the sea-bottom and
a secondary coil on a lightship, in combination with apparatus for calling attention
and signalling by means of discontinuous or alternate currents; for the purpose set.
forth and substantially as described.
(2) A cumulative-impulse relay comprising a circuit to receive an alternate
current, and a vibrator adapted to be set in vibration by and in unison with the
said current and thereby to close a circuit; for the purpose set forth and substan-
tially as described.
(3) A cumulative-impulse relay made substantially as described, and illustrated.
in Fig. 4.
(4) A cumulative-impulse relay comprising two similar conducting wires free to
vibrate in a fixed magnetic field and adapted to receive and vibrate in unison with.
alternate currents of given frequency and thereby to close a circuit; for the
purposes set forth and substantially as described, and illustrated in Fig. 5.
Dated this 27th day of March 1893.
SYDNEY EVERSHED.