IMPROVEMENTS IN ELECTRICAL SIGNALLING APPARATUS
Year: 1879

page_text: LETTERS PATENT to Alexander Melville Clark, of 53, Chancery Lane, in the
County of Middlesex, Patent Agent, for the Invention of "IMPROVEMENTS
IN ELECTRICAL SIGNALLING APPARATUS." A communication from abroad by
William Hadden, of the City, County, and State of New York, United States
of America.
Sealed the 21st November 1879, and dated the 24th September 1879.
COMPLETE SPECIFICATION filed by the said Alexander Melville Clark at the
Office of the Commissioners of Patents on the 24th September 1879.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex,
Patent Agent.
“IMPROVEMENTS IN ELECTRICAL SIGNALLING APPARATUS." A
communication from abroad by William Hadden, of the City, County, and State
of New York, United States of America.
The object of this Invention is to furnish an improved signalling apparatus for
closing and breaking an electric circuit a prescribed number of times to indicate a
locality, a want, or any other thing, and for controlling the current and counter-
acting or neutralizing the effect which any escape on the main line may produce
upon the sensitive paper used in the receiving instrument.
The Invention consists in a signalling device consisting of a non-conducting
trough having two wires connected with two corresponding series of exposed contact
points in the bottom of the trough in combination with a separate metallic circuit
closer having a bifurcated end; in the rheostat, formed of a non-conducting tube
filled with carbon powder to adapt it to be applied to the circuit wires of a battery;
and in the combination of a local circuit and a rheostat with the line circuit of a
district telegraph signalling apparatus, as herein after fully described.
In most signalling devices a clock mechanism or other motor is used to cause a
movement of the parts which make and break the circuit, and such complication
usually attends such arrangements as to involve always more or less liability to
derangement, which may result in the permanent closing of the circuit and the
throwing of all the other like instruments out of working condition.

page_text: The signalling device of this Invention is designed to reduce this liability to
derangement, and to simplify the construction and use, and lessen the cost of such
signalling device, and to this end I employ a plain non-conducting trough having
in its groove or channel paired contact points arranged in groups of arbitrary
numbers, in which all the contacts upon one side are connected with one end of the
line wire, and those upon the other side are connected with the other end of the line
wire in connection with a separate 'metallic connecting plate having its ends slotted
and adapted to fit into the channel of the trough, so that when it is moved down
over the contact points it will make and break the electric circuit in accordance
with the number of the contact points and in the order of the grouping, to give
either a written or an alarm signal, as may be required.
In the accompanying Drawings, Figure 1 is a view illustrating the arrangement
of the improved apparatus; Figure is a longitudinal section of the signalling
device, taken through the line x-x, Figure 1; Figure 3 is a cross section of the
same taken through the line y-y, Figure 1. A represents a non conducting trough,
along the back of which extend two conducting wires B, B', connected with the
two ends of the line wire F, FI, on the two poles of the battery. These wires B, B',
are normally disconnected, but have exposed in the bottom of the trough A the
elongated contact surfaces C, C, and the contact points D, D¹, D². E is a metal
circuit closer, which is an entirely separate and distinct piece having a bifurcated
end whose branches are adapted to slide over the contact points. In using the
device the circuit closing plate E is taken in the hand, its slotted end is applied to
the top of the trough A, and it is steadily moved down to the bottom of the trough
⚫ over the contact points. If the record is to be received upon sensitive paper which
is moved by a clock mechanism the current closer is applied above the contact
surfaces C, C¹, which are elongated to give a longer time for the initial closing of
the circuit, in order that the magnet at the receiving end may have time to dis-
engage the details of the mechanism which controls the movement of the paper.
If a bell signal is all that is required the circuit closer E may be applied below the
contact surfaces C, C¹, and may be moved only over the contact points D, D', D².
The contact points may be arranged in groups of any size or number; but, as shown,
there are three groups of two pairs at D, three pairs at D¹, and two pairs at D²,
making the record 2, 3, 2, when such points are necessarily closed by the downward
stroke of the plate E. Now in defining the Invention with greater distinctness I
would state that the separate character of the plate E permits any degree of pressure
to be applied by hand, insuring a rubbing action and a pure electrical contact. On
the other hand, when not in use it is entirely disconnected from the contact points,
and can never from accidental causes or the derangement of parts obstruct the
.signals of other instruments by permanently closing the line. These distinctions,
together with the simple construction and trifling cost, make the device very far
superior to signalling devices in which the moving parts are permanently organised
in a single instrument, and are not separable. Now I do not claim broadly a device
for making and breaking contact in which a series of conducting and non conducting
spaces are traversed by a conducting stylus, as I am aware that these have been
employed as a means for recording an alphabet. I do not know however that a
split or bifurcated circuit closing plate E has been used in connection with a non-
conducting trough having on its channel two series of contact points, between which
the circuit is closed by the slotted plate. The merit of the slotted plate is that
each branch springs down independently upon its row of contacts, and always closes
the circuit, through any pair of contact points, by the passage of the current through
the handle or unslotted portion, it being obvious that if the plate were not slotted
one contact point might project more than its mate, and the plate in sliding over
the higher one would fail to touch the lower, and the circuit would not be closed.
By making the non-conducting frame A in the form of a trough the sides of the
latter guide the prongs or branches of the circuit closer, and do not allow them to
pass laterally off of the said contacts. G represents the batteries of the line wire
F, F. H represents the conductor, from which the current passes through the

page_text: "
sensitive paper to the roller I over which the said sensitive paper passes, and thence
back to the line wire. J represents the battery and K the wire of a local circuit
so arranged by opposing the poles of the local battery to the main line battery
as to counteract or neutralize the effect of any "escape on the main line, which
escape might be sufficient to prevent the formation of the distinctive marks to be
made by the action of the signal instrument upon the paper in the receiving instru-
ment. To allow the force of the local current to be regulated so as to exactly
counteract or neutralize the amount of escape upon the main line circuit, and thus
clear the sensitive paper from the mark produced by such "escape," I connect the
local circuit wire K with a rheostat, so that I may vary the resistance in the local
circuit, and thus increase or weaken the effect of the local battery, as may be
required. The rheostat shown in the Drawings, and which I prefer to use, consists
of a tube L of glass or other suitable nonconducting material filled with carbon
powder M, such as plumbago or other conducting powder. One end of the wire K
is permanently secured in one end of the glass tube L and the other end of the said
wire K enters the other end of the glass tube L, and is movable, so that it may be
slid out and in to bring it into contact with the stationary end of the wire, or adjust
it at any desired distance from the said stationary end to increase or diminish the
resistance to the local circuit as may be required.
Having described the nature of the said Invention, and the manner of performing
the same, I declare that what I claim as new and desire to secure by Letters
Patent is,―
1st. A signalling device consisting of a non conducting trough A having wires
B, B¹, connected with two corresponding series of exposed contact points in the
bottom of trough in combination with a separate metallic circuit closer E having a
bifurcated end, substantially as herein shown and described.
2nd. The rheostat formed of a non conducting tube L filled with carbon powder M
to adapt it to be applied to the circuit wires of a battery, substantially as herein
shown and described.
3rd. The combination of a local circuit J, K, and an adjustable rheostat L, M,
with the line circuit C, F, F¹, of a district telegraph signalling apparatus, substan-
tially as herein shown and described.
In witness whereof, I, the said Alexander Melville Clark, have hereunto set
my hand and seal, this Twenty-fourth day of September, in the year of our
Lord One thousand eight hundred and seventy-nine.
AT DE