Improvements relating to the Transmission of Telephonic Messages Between the Shore and a Lighthouse, Ship, or other Signal Station.
Year: 1894

page_text: Date of Application, 25th Sept., 1894-Accepted, 19th Jan., 1895
COMPLETE SPECIFICATION.
Improvements relating to the Transmission of Telephonic Messages
Between the Shore and a Lighthouse, Ship, or other Signal
Station.
I, LUCIEN IRA BLAKE, residing at Lawrence, in the County of Douglas, and
State of Kansas, United States of America Professor of Physics, in the University
of Kansas, do hereby declare the nature of this invention and in what manner
the same is to lie performed to be particularly described and ascertained in and
by the following statement :-
It was well known prior to my invention that electric currents suitable for
operating sensitive signalling instruments could be transmitted through an insulated
metallic conductor submerged in the water or buried in the earth, even though the
conductor contained a break, the continuity of the conducting path for a short
distance being preserved by the water or the moist earth between the terminals of
the conductor at the break.
It has moreover been proposed to take advantage of this fact in systems of
electric signalling between the shore and lightships or isolated lighthouses by
running from a shore station two insulated cables forming the lead and return of a
signalling circuit, leaving their exposed ends near the ship and on opposite sides of
the same, and partially bridging said ends by a conductor carried by the ship and
including a signalling instrument. In this and similar cases the object in view was
to so far complete the metallic circuit that, although a portion of the current would
pass between the terminals of the insulated conductor through the water, a sufficient
amount would pass through the bridging conductor to affect a delicate signalling
instrument connected therewith. So far as I am aware, no practically successful
results have been secured by the systems of this nature heretofore proposed, nor
has the transmission of articulate speech under such conditions ever been
accomplished.
It is also a recognized fact in science, if the two terminals of an electric circuit
from a source of current be immersed in a body of water, that around each of them
for a certain distance an electrified or active region will be established in which
but the
there will exist a difference of potential between different points;
information with regard to this phenomenon has not, so far as I am aware, been
sufficient to lead to or even suggest the possibility of taking advantage of it in any
system for the practical transmission between two points of articulate speech.
I have, however, discovered a practical method of transmitting articulate speech
on this principle, which I apply to communicating between a shore station and a
lightship or any other vessel or station, by establishing under and around the ship
or station a large electrified region between the different parts of which there
exists a suitable difference of potential, and providing a metallic conductor to be
carried by the ship and the ends of which may be immersed in such region to
connect two points therein between which such difference of potential exists.
have found when the conditions hereinafter stated are properly observed, that a
suitable telephone included in the circuit of the conductor carried by the ship will
respond to variations of potential between any two points in the electrified region,
and that when such variations are caused by the voice of a person speaking into a
suitable telephonic transmitter the words may be clearly produced. Further, I have
I

page_text: proven by experiment that it is possible to greatly extend this electrified region
and to obtain it in different forms suitable for special purposes as will be hereinafter
described.
In order to describe in detail the manner in which I have carried out my
invention I now refer to the accompanying drawings in which
Fig. 1 is a diagram of the general plan of carrying out the invention.
Fig. 2 is a similar diagram of a modification of the same.
In Fig. 1 which illustrates the general plan which I have followed in practising
the invention, A designates a shore station, and S a station more or less remote
therefrom, and which is or may be a lightship, or any other vessel or the like.
At the station A, is a battery B, a telephonic transmitter C, and a receiver D.
The batteries and telephones may be and in the present case are shown as connected
up in a local circuit, the line being a secondary or induced circuit through the
secondary, F, of a suitable stepdown induction coil or one in which a current of
high potential in the primary is converted to a current of lower potential in the
secondary.
In the claims hereto annexed, although these transformers are not specified as
an element, it will be understood that they are to be considered as included where
their presence, by reason of the length of cable or insulated line, or the extent of
the region of communication, is rendered desirable or necessary. It will also be
understood that the said transformers inay be located at any proper point in the
circuit to produce the desired effects.
The line is an insulated cable or conductor, G, grounded at E at or near the shore
station A, and extended out as indicated to the desired location of the electric
region to a submerged plate or conducting body, which in the present instance is
shown as the anchor E, of the vessel S.
If the electrified area of communication is to be at a long distance from the
shore, the step-down transformer is preferably placed at or near the point where
the cable is bared or grounded for the purpose of producing such electrification of
the water; and in such case, of course, a step-up transformer may be used at the
shore station in order to increase the potential necessary to carry the impulses
through the long line. The object in using the step-down transformer is to reduce
the potential and correspondingly increase the quantity of the current throughout
the electrified area; since the extent of this electrified area will depend largely
upon the strength of the current.
It appears with the arrangement illustrated, and when electric impulses are
transmitted over the circuit, that an active or electrified region, which may be
designated the region of communication, is established in the water around each
terminal plate, and that a difference of potential exists between any two points
therein at unequal distances from either terminal plate. The two immersed terminals
of the cable may be at a very considerable distance apart even to many miles and
wholly independent of each other, so that no current actually flows from one to the
other; but if from any vessel as S, lying at any point in one of these regions of
communication, the ends of a conductor K be let down into the water so that it
connects two points at unequal distances from either terininal E and E¹, electric
impulses will pass in said conductor corresponding to those transmitted through the
cable from the shore station A. A suitable telephonie receiver in the conductor K
will reproduce the signals or speed thus transmitted.
Instead of including the transmitter on the ship directly in the conductor K, it
is desirable to employ a transmitter C' and a battery B' in a local circuit including
the primary coil of an induction coil, the coil of low resistance of which is in the
circuit of conductor K.
I have found it necessary, however, in order to transmit speech in this way to
employ telephonic receivers specially constructed of exceedingly low resistance, in
comparison with ordinary telephones, and determined for each case by the size of
the terminal plates of the conductor K, and the specific conductivity of the medium
in which they are immersed.

page_text: The resistance of telephonic receivers as used for ordinary commercial purposes
varies from 75 to 100 ohms. I find it expedient ordinarily to employ a telephone in
my receiving circuit whose resistance will be as low as one ohm, or, preferably less
than this-even as low as one-fortieth of an ohm. Such a telephone is readily
made by using a larger wire than that used on the ordinary telephone, and decreasing
the number of turns.
The resistance of my receiving telephone, as above indicated, will also be
determined to some extent by the nature of the medium in which the work is being
carried on. The resistance of salt water being many times less than that of fresh
water (approximately stated, as 1 to 50), it follows that, with a given distance
between the terminal plates of the receiving circuit, there will be a greater difference
of potential in fresh water than in salt, and consequently a higher resistance can
be permitted in the receiving circuit as a whole, and of course in the receiving
telephone as part of such circuit.
So, also, the size of the terminal plates of the receiving circuit should be made
as large as possible, in order to reduce the total resistance of that circuit; and the
lower the total resistance of such circuit the lower should be the resistance of the
telephone forming a part of it.
It is not only possible to transmit in this way signals from the shore to a ship,
but also from the ship to the shore.
The region of communication may be greatly extended and directed by exposing
the conductor of the insulated cable at suitable intervals, or providing local
terminal plates M at intervals along its course as shown in Fig. 2, or employing a
bare conductor M' in lieu of the plates. In this case each plate or exposed portion
of the conductor serves as a terminal or point from which the electrical influence
is diffused.
In practice I have found that with a bare copper wire of suitable low resistance,
I can develop the region of communication for about a mile or more along the
direction of the wire and for several hundred feet all around it, and obtain in a
telephonic receiver D' clearly audible speech when the ends of a short conductor K
including the same are immersed at any two points in the body of water unequally
distant from the wire and within the above limits.
The length of the conductor K may be very short compared with the total
distance between the terminals of the cable, and the length of an ordinary ship is
ample to secure good results.
The utility of my discovery is apparent. For not only does it afford a practical
means of maintaining communication with isolated lighthouses, or permanently
anchored lightships, but with any incoming or outgoing vessel which may be
equipped with the necessary apparatus, and while within the limits of a " region of
communication." These regions may for convenience be indicated by buoys or
the like, and may be located many miles out at sea.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, 1 declare that what 1
claim is-
1. The combination with a source of current, and transmitting instruments at a
shore station and an insulated submarine conductor or cable bared or exposed to
the water at two or more points so as to establish an electrified region of communi-
cation, of a conductor having its ends immersed at two points of different potential
in said area and a telephone of low resistance in circuit therewith, said telephone
and conductor being carried by a lightship or other vessel, or connected with a
lighthouse or other signal station, as set forth.
2. The combination with a source of current, and signalling instruments located
at a shore station, and a submerged cable or insulated conductor extending from
such station and grounded or exposed to the water at said station and at intervals
along its course, of a conductor having its ends immersed at two points unequally
distant from any one of the points at which the cable is exposed, and signalling

page_text: instruments connected with said conductor, the said instruments and conductor
being carried by a lightship or other vessel, or connected with a lighthouse or other
signal station, as set forth.
Dated this 25th day of September 1894.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.