IMPROVEMENTS IN REPEATERS FOR SUBMARINE CABLES
Year: 1885

page_text: "
I, MOSES GERRISII FARMER of Newport, Rhode Island, United States of
America, Electrical Engineer, do hereby declare the nature of my invention for
IMPROVEMENTS IN REPEATERS FOR SUBMARINE CABLES" and in what manner
the same is to be performed, to be particularly described and ascertained in and
by the following statement:-
It is well known that the capacity of long submarine cables is very limited in
comparison with aerial lines of equal length.-For instance in a cable say 2000
miles or more in length, it is impraticable to transmit messages at a greater rate
of speed than twenty-five or thirty words per minute, and this with the most
approved forms of the mirror instrument. With instruments of a less sensitive
character, the rate is very much less, for instance with the Morse apparatus the
speed of practicable transmission is limited to two or three words per minute.
In contrast to this necessarily slow rate is that over aerial lines which may reach
250 words per minute over a line at least 2000 miles long.
It has been found that the speed of transmission through submarine or similar
cables varies inversely as the square of the length of the line, so that if two words
per minute could be transmitted through a cable 2000 miles in length, eight words
could be sent in the same time over a cable half as long; thirty-two words over a
cable one-fourth as long, and two hundred words over a cable one-tenth as long, or
two hundred miles, the speed of transmission under such circumstances being
limited to the efficiency of the operators or signalling apparatus rather than to the
retardation encountered in the line. The capacity of a cable, therefore, could be
increased by dividing it into two or more sections and repeating the signals from
one section to the other by apparatus used between the sections at the repeating
stations.
The object of my invention is to provide practicable and efficient means for
accomplishing this result.
Heretofore it has not been found practicable to employ more than one repeating
station or repeating apparatus in submarine cables, if any, partly on account of
defective construction of the apparatus proposed for this purpose, but mainly on
account of the impracticability if not impossibility of providing for a local current
to be used at the repeating station.
This difficulty, however, I have overcome by the employment of two wires or
lines, I shall more fully hereinafter describe.
The other main difficulties hitherto met in all ordinary forms of repeater, are the
necessity for constant adjustment and the rapid deterioration of the instruments
due to oxidation of the points of contact and like causes, but these also I have

page_text: obviated by the novel construction and mode of operation of the instruments
which I have devised.
I will describe first the general nature of the apparatus which forms the subject
of my invention, and then indicate more in detail the particular features of novelty
which distinguish the same.
I use a cable with two wires or lines insulated throughout, and it may be here
stated that as the invention applies more particularly to what are commonly known
as submarine cables, the construction of which is well understood and largely a
matter of choice, no further description of the precise construction of cable is
given. One of the wires is not divided into sections, but forms an unbroken
circuit throughout its whole length. The other wire or line, which, to distinguish
it from the first or continuous line is herein designated the main line, operates the
signalling apparatus.
These consist in the main of a transmitter and receiver at each end, a relay at
each repeating station that makes and breaks, or preferably reverses the current in
one of the branches of the local circuit in which is contained the primary of an
induction coil, and secondary coils in which impulses of current are induced by the
primaries in the continuous circuit. I also use certain accessories for controlling
the direction of signalling and for neutralizing the effects of the earth's electricity
and the like, which will be hereinafter referred to.
The first section of the main line enters the first repeating station, which is a
water-tight box containing the necessary apparatus and connected directly to the
cable and there connects to a switch controlled by the polarized armature of an
electro-maguet in a branch of the continuous line. One portion of this switch
carries the main line to a magnet controlling by means of a polarized armature a
circuit reverser in the other branch of the continuous line from which magnet the
line goes to earth. In the branch of the continuous line with the circuit reverser
is also the primary of an induction coil. The secondary coil has one end grounded,
and the other connected to the second section of the main line through the polarized
switch when the latter is in the position just described. The other repeating
stations are like the first, and it is obvious that an electrical impulse in the first
section of the main operates the circuit reverser in the local branch of the continuous
line, and induces thereby a corresponding impulse in the second section of the main,
and so on.
The purpose of the polarized switch is to control the direction of transmission,
for by reversing the direction of current in the continuous line the switch is shifted
to its second position by which the first section of the main is taken to earth
through the secondary of the induction coil while the second is carried to earth
through the magnet that operates the circuit reverser, in other words the section of
main wire that previously transmitted the impulses to the next, now receives them,
and so to all the other sections, however many there may be.
It is desirable to use condensers in the main line between the secondary coil and
the earth, or between the other end of the secondary and the cable, or both. Such
use of the condensers frees the line from the influence of earth currents, partially
or wholly, but it is not essential to the operation of the system.
Referring now to the drawing, by means of which the invention will be under-
stood in detail.
Fig. 1, is a diagram of the terminal apparatus of the line, in the condition in
which it remains while signals are being transmitted therefrom.
Fig. 2, is a diagram of the terminal apparatus at the time of receiving.
Fig. 3, is a plan view of the repeating box or station.
Fig. 4, is a diagram of the circuit with the inactive portions omitted, showing
the mode of using the condenser.
Fig. 5, is a similar diagram with fewer condensers.
Similar letters and characters indicate corresponding parts in all the figures.
In Fig. 1, which represents for the time being the transmitting station, B, designates
the large battery for charging the local line L. By wire c it is grounded at 1.

page_text: A switch S connects the continuous line L with its opposite pole or with a shunt c²
around the battery to wire c. M, designates the main line over which signals are
sent. It is grounded at 2 through a switch E, and the secondary of an induction
coil A. The primary of this instrument is a circuit a, containing a circuit reverser.
The latter device consists of a metal block a¹, between two pivotted levers b and b¹;
by springs these levers are drawn towards each other with a tendency to come
into contact with the block a B2 is a pivotted lever carrying a polarized armature.
To the end of this lever is fixed an arm or plate B³, between the two levers b and b²,
and of slightly greater width than the plate or block al. Lever B is held in a
position at right angles to plate a¹, by means of opposing springs a², and when in
this position it touches both levers while they are also in contact with the plate a¹.
The wires from the battery C connect to lever B and plate a¹, respectively, and
the ends of the wire including the primary of coil A. are connected to the levers b, b¹,
as shown.
The polarized armature is actuated by an electro-magnet D in a circuit d
containing a signalling instrument operated by drawing a perforated strip or
tape d' between two contact points, or by any other device for producing makes
and breaks or reversals of the circuit.
These impulses of current actuate the armature B2 and send corresponding
impulses through the circuit a, for either one or the other of the levers b, b¹, is
brought by the movement of the armature into contact with the plate a¹, while
the parts may be so adjusted that a direct current impulse will produce a reversal
in circuit a, by the momentum of the lever B³ on its backward movement. A more
positive movement of this lever would be produced by a reversal of current in the
magnet D.
These impulses or reversals induce corresponding impulses in the secondary coil
of the induction coil A, which go to line M, and are received at the other end after
being repeated at the repeating stations as hereinafter described.
Fig. 2, represents the receiving station for the time being.
The instruments are in every respect similar to those at the transmitting station,
but the battery B¹ of the continuous line is cut out by turning the switch S¹ on to
the shunt wire c³, and the transmitting apparatus is disconnected from the main
line switch E', while by the same switch the main line is grounded through the
relay of the receiving apparatus.
This apparatus consists of a polarized relay F, the armature of which is in a
local circuit f, and vibrates between stops f³, ƒ'. A switch e is used to connect
either stop f¹ with the local, so that dots or dashes may be read from the chemical
receiver G instead of spaces. Any ordinary form of chemical receiver may be used
in the local f.
Fig. 3, illustrates one of the repeating stations. As above stated I enclose the
apparatus in a strong water-tight box which is represented by the dotted line G¹.
The cable is severed at the point where it is desired to insert a repeater and its
ends joined to the box by proper splicing. In each of the boxes or stations are
two instruments which may be designated as the director and the repeater. They
are both in construction similar in every essential particular to the transmitting
apparatus which I have already described, except that I prefer to use in place of
the springs 63, 62, a permanent horse-shoe magnet H. This magnet is clamped to a
suitable base with its poles close to the ends of the levers corresponding to b, b',
which are bent at right angles and made of soft iron so that the effect of the
magnetic attraction upon them will be the same as that of the springs b². The
wires of the cable are carried into and out of the box at the two points h, h¹.
The wire L is branched after entering the box. One branch L¹ passes through the
coils of the directing magnet I, beyond which it joins the other branch L¹¹, the
path of which is through the armature lever Ň of the repeater magnet K,
the plate n', and from one of levers i, i', to the other through the primary of an
induction coil A¹.

page_text: '
The main wire M after entering the box is connected to the armature lever N¹ of
the director magnet I. From one of the levers as m¹, a wire M' leads to and includes
the magnet K, and is then carried out through the box and attached to a plate 3,
It is
or otherwise grounded. From the other lever m, a wire M" is taken.
connected with the secondary of the induction coil A¹, and then grounded. Suppose
it be desired to transmit signals from the side of the repeating station at which the
cable enters at h, the mode of operation and the condition of the apparatus are as
follows-One pole of the battery B, say the positive, is connected to the line L by
the switch S. The battery at the other end, the positive pole of which is also
adapted to be connected to line L by switch S, is disconnected as shown in Fig. 2.
The current entering the repeating station on this line divides, part passing through
the coils of magnet I, and the rest through the primary of induction coil A'. The
effect upon the polarized armature is to move the lever m¹ away from plate o,
leaving the other lever m in contact with the plate. This carries the main line M
through the coils of magnet K, and grounds it at 3. An impulse of current
coming over the line sets in motion the lever 'N, and reverses the current in the
local branch L", and through the primary of induction coil A¹. The impulse
induced in the secondary of the coil by this means passes through the ground
wire M, to lever m, thence through plate o, and off through the second section of
the main wire M to the next repeating station, where the same operation is
repeated.
If now it be desired to tramit signals in the opposite direction, the battery B
is disconnected and B connected with the line L, so that a current will flow therein
in an opposite direction. The polarized armature of magnet I, in this event tilts
lever N to a position in which lever m¹ is in contact with plate o, and lever m
forced away from it. The branch M¹ will operate the magnet K as before; the
currents induced in the secondary of induction coil A¹, will however flow through
wire M, lever m, and lever N to line.
Figs. 4 and 5, show the general arrangement of the system and the relations of
the several parts of the same, but for convenience the receiving apparatus at the
left hand end of the line, and the transmitting apparatus at the other, are omitted.
For the same reason one repeating station only is shown, but the others, when used,
are connected to the cable in a precisely similar manner.
In order to prevent the interference of earth currents, I sometimes insert a
condenser in the main line at both ends of each section as shown in Fig. 4, or at one
end only, as in Fig. 5.
In order to render the system more practicable, certain conditions should be
observed. Wherever in a line separable contact points occur, they should be of
iridum, or some metal possessing like qualities, for although an actual make and
break can be avoided by the construction and mode of operation which I have set
forth, there is still a possibility of exposed metallic surfaces becoming oxidized,
which is present to a very slight degree in the case of iridium.
It is also inadvisable to rely upon single points of contact. All separable
contacts, therefore, should be multiple; for instance, in lieu of using a single
lever as bor 61, a number of levers with a common pivotted shaft should be
employed.
With reference to specific details of construction, I would state that for a better
understanding of the nature of the invention, I have illustrated many parts by the
ordinary conventional representations that are used therefor. In constructing the
apparatus for practical use, however, the relations and adjustments must be fixed
and permanent, and the apparatus differs from others of like nature in being so
constructed that there will be the least possibility of any alteration taking place.
The movable parts must be carefully balanced so that their operation will be
entirely unaffected by the position in which they are held. The enclosing boxes
should have great strength combined with lightness, so as to be capable of with-
standing rough usage. It is desirable to construct the sections of cable that contain

page_text: the repeating boxes with special reference to the usage to which they are likely to
be subjected, and to splice them to the main sections.
With reference to certain features not specifically described herein, it may be
stated that much pertaining to them is left to the discretion of practical users.
For instance, it is largely a matter of choice in what manner the transmitting and
receiving instruments at the ends of the line are constructed or used, and in what
way or by what means the local line is supplied with the requisite current.
The main feature of the invention consists in repeating signals through the
instrumentality of induction coils, the primaries of which are included in an
unbroken circuit co-extensive with the signalling line or the sections thereof, and
by producing such electrical changes in each primary coil as will induce impulses
in the secondaries. The other parts of the invention consist in the means for
accomplishing this and in the accessory devices that contribute to their proper and
successful operation.
Having now particularly described and ascertained the nature of my said
Invention, and in what manner the same is to be performed, I declare that what
I claim is
1. The combination with a cable containing a continuous line and a sectional
main line or wire, of one or more devices for repeating signals from one section of
the main to another, each consisting of a primary coil in the continuous line, means
for reversing the direction of current through the coil connected with and operated
by one section of the main and a secondary coil in the next succeeding section, all
Bubstantially as set forth.
2. The combination with a cable containing a continuous line and a sectional
main line or wire, of one or more devices for repeating signals from one section to
another, each consisting of a primary coil in the continuous line, means for
reversing the direction of current through the coil included in one section of the
main, a secondary coil in the next succeeding section, and apparatus operated by
the local for transferring the circuit reverser and secondary coil from one section of
the main to the other, all substantially as set forth.
3. A repeater for submarine electric cables consisting of the following instru-
mentalities, to wit:-An induction coil, means for reversing the direction of the
current through its primary, an electro-magnet for controlling the same independent
of the primary coil, and an electro-magnetic switch or director in a branch of the
primary circuit for connecting the said magnet and the secondary coil with either
of two circuits respectively, all as set forth.
4. The combination with a cable containing a continuous line and a sectional
main wire, or line, of one or more devices for repeating signals from one section of
the main to the next, consisting of a primary coil in a branch of the continuous
line, means for reversing the direction of current in said branch included in one
section of the main, a secondary coil in the next succeeding section and an electro-
magnetic switch or director included in a second branch of the continuous line for
transferring the circuit reverser and secondary coil from one section to the other,
all substantially as set forth.
5. The combination with an electrical cable containing a continuous line and a
sectional main wire or line, of one or more devices for repeating signals from one
section of the main to the next, each consisting of a primary coil in a branch of
the continuous line, a device for reversing the current through said branch, a
magnet in one section of the main for controlling said device, a secondary coil in
the next succeeding section and an electro-magnetic switch or director for grounding
the sections through the secondary and the circuit reverser respectively, as and for
the purpose specified.
6. The combination with an electrical cable containing a continuous line and a
sectional main wire or line, of one or more repeaters consisting of a primary coil in
a branch of the continuous line, a device for reversing the current through said
branch, a magnet in one section of the main for controlling said device, a secondary

page_text: coil in the next, an electro-magnet with polarized armature in a second branch of
the local and a switch or director for grounding the sections through the secondary
and the circuit reverser respectively, all as set forth.
7. The combination with a cable containing a continuous line and a sectional
main line or wire, of one or more repeaters consisting of a primary coil in the
continuous line, a circuit reverser for changing the direction of the current in the
primary and connected with one section of the main, a secondary coil included, in
the next succeeding section, and condensers inserted in the sections of the main as
and for the purpose specified.
8th The combination with a grounded section of a main line M, a magnet K
included therein, and a circuit reverser operated by the said magnet, of a primary
coil in a circuit co-extensive with the main line, the current in which is sent
through the primary in opposite directions by the circuit reverser, and a secondary
coil in the next branch of the main line M, all substantially as set forth.
9th The combination with a cable containing a continuous line and a sectional
main line, of a primary coil in the continuous line, means for reversing the direction
of current through the coil, an electro-magnet for controlling said means included
in one section of the main line, and a secondary coil in the next section, the sections
being grounded through the magnet and secondary respectively, as set forth.
ALLISON BROS,
Agents for the Applicant.