IM- PROVEMENTS IN THE MODE OF AND APPARATUS FOR SIGNALLING ON RAIL- WAYS.
Year: 1873

page_text: LETTERS PATENT to William Henry Precce, of the Town and County
of Southampton, Electrical Engineer, for the Invention of "IM-
PROVEMENTS IN THE MODE OF AND APPARATUS FOR SIGNALLING ON RAIL-
WAYS.
"
Sealed the 1st July 1873, and dated the 14th January 1873.
PROVISIONAL SPECIFICATION left by the said William Henry Preece
at the Office of the Commissioners of Patents, with his Petition,
on the 14th January 1873.
I, WILLIAM HENRY PREECE, of the Town and County of South-
ampton, Electrical Engineer, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN THE MODE OF AND APPARATUS FOR SIGNALLING
ON RAILWAYS," to be as follows :—
The chief object of this Invention is to work semaphore instruments
with one line wire without rendering them liable to be affected by
lighting contact, or other disturbing electrical influences. To this
end I make the release of the semaphore when standing at "danger"

page_text: dependent upon the co-operation of the signalmen at the opposite ends
of a section of railway. The attendant at one end preparing for the fall
of the semaphore and the other effecting its fall.
The apparatus which I employ for this purpose is provided with two.
electro-magnets through one of which, by reason of its connection with
the line wire, the distant current passes, while the other is caused to
act by connection with a local battery; the semaphore is mounted on a
pivot and is counterbalanced, and affixed to the pivot is a slotted disc,
in the slot of which works a pin that is carried by a vertical rod. The
lower end of this rod is jointed to a crank arm on the pivot of an
induced magnet, which rocks between the poles of the electro-magnet
in connection with the line wire. By means of this electro-magnet the
rod is caused to sustain the disc and through it the semaphore in the
"danger" position. On the electro-magnet ceasing to act the rod will
fall and leave the semaphore free to fall also, but that it is otherwise
sustained. The sustaining of the semaphore in position is effected by
means of a rod projecting from the armature of the second electro-
magnet; which rod acts as a prop to support a finger or projection
on the pivot of the semaphore. This second electro-magnet when set
in action by the depression of a key (which completes the circuit of the
local battery) attracts the armature and withdraws the prop from under
the finger of the pivot. The semaphore will therefore drop by its own
weight, and indicate that the line is clear.
In order to set the instrument at "danger," the electro-magnet of the
line wire is brought into action, when through the rocking of the
induced magnet the rod in connection therewith will be caused to lift
the semaphore, and acting as a detent maintain it in position. The
local circuit being now broken the armature of the electro-magnet in
that circuit will be drawn back by the tension of a spring attached
thereto, and its rod will again act as a prop to sustain the semaphore
in position when the detent rod has dropped out of action.
In operating with this instrument an audible signal will be used to
inform the man at the home station that his detent rod is dropped out
of action, and he will then in acknowledging the signal send a current
through the home circuit to withdraw the support from the semaphore.
It will be obvious that instead of the man at the distant station
preparing for the change of position of the semaphore, he may actuate

page_text: one of a pair of arms leaving the signal to be completed by the lowering
of the other arm by the man at the home station.
In order to prevent two opposing currents from neutralizing cach
other, and thus obstruct the action of the semaphore or other signalling
apparatus, when one line wire only is used, I provide at each station
apparatus for dividing the current on the principle of the differential
galvanometer or Wheatston's bridge, and thus cause the unneutralized
half of the opposed current to do the work by acting on the armature
connected with the semaphore,
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said William Henry Preece in the Great Scal
Patent Office on the 14th July 1873.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
HENRY PREECE, of the Town and County of Southampton, Electrical
Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Fourteenth day of January, in the year
of our Lord One thousand eight hundred and seventy-three, in the
thirty-sixth year of Her reign, did, for Herself, Her heirs and suc-
cessors, give and grant unto me, the said William Henry Preece, Her
special licence that I, the said William Henry Precce, my executors,
administrators, and assigns, or such others as I, the said William
Henry Preece, my executors, 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 In-
vention for "IMPROVEMENTS IN THE MODE OF AND APPARATUS FOR SIGNALLING
ON RAILWAYS," upon the condition (amongst others) that I, the said
William Henry Preece, my executors or administrators, by an instru-
ment in writing under my, or their, or one of their hands and seals,
should particularly describe and ascertain the nature of the said In-
vention, and in what manner the same was to be performed, and cause.

page_text: the same to be filed in the Great Seal Patent Office within six calendar
months next and immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said William Henry Preece, do
hereby declare the nature of my said Invention, and in what manner
the same is to be performed, to be particularly described and ascertained
in and by the following statement, reference being had to the Drawing
hereunto annexed, and to the letters and figures marked thereon (that is
to say) :—
The chief object of this Invention is to work semaphore instruments
with one line wire without risk of the signals being affected by
lightening contact or other disturbing electrical influences. To this end I
make the release of the semaphore when standing at "danger" dependent
upon the co-operation of the signalmen at the opposite ends of a section
of railway, the attendant at one end preparing for the fall of the sema-
phore and the other effecting its fall.
The apparatus which I employ for this purpose is shewn in several
views in the accompanying Drawing, the enclosing case being removed
to expose the details of construction, and explain the action of the
parts.
I would also remark that to render the Invention the more clear, 1
I have omitted all the parts relating to the transmission of audible
signals; which parts will in general be combined in the same instru-
ment with my Invention.
Fig. 1 is a back elevation of the instrument, shewing the semaphore
arm locked at "danger;" Fig. 2 is a similar view, but with the instrument
prepared for the fall of the semaphore; Fig. 3 is a view shewing the
semaphore released.
The instrument it will be seen is provided with two electro-magnets
A and B, through one of which (A), by means of its connection with
the line wire, the distant current passes, while the other (B) is caused a
to act by connection with a local battery. The electro-magnet A is
composed of a permanent magnet between two arms of which (a, b,)
(constituting the poles of the electro-magnet) a bar of soft iron A¹
vibrates; C is the semaphore mounted on a pivot c and counterbalanced
by an adjustable weight; affixed to the pivot c is a slotted disc d; in the a

page_text: "
slot of this disc works a pin that is carried by a vertical rod e, the
lower end of which rod is jointed to a crank arm on the pivot of the
bar of soft iron A' which rocks between the poles a, b, of the magnet A,
the coils of which are connected with the line wire. By the action
of the electro-magnet on the vibrating bar A¹ to bring it into the
position shewn at Fig. 1, the rod e will be raised and caused to rock
the disc d, and thereby raise the semaphore and sustain it in the
'danger" position. On the clectric current being reversed the
vibrating bar A₁ will be thrown into the position of Fig. 2, when
the rode will fall and leave the semaphore free to fall also, but that
it is otherwise sustained. The sustaining of the semaphore in the
danger" position is effected by means of a rod extending from the
armature D of the second electro-magnet B, which rod acts as a
prop to support a finger or projection fon the pivot c of the semaphore.
For this purpose it is connected to a tension spring which retains it
in position for supporting the semaphore until acted on by the electro-
magnet B. When however this magnet is set in action, which is done
by the depression of a key, as shewn at E, completing the circuit of the
local battery, it will attract the armature and thereby withdraw the
prop from under the finger f of the pivot. The semaphore will therefore
drop by its own weight into the position of Fig. 3, and indicate that the
line is clear.
66
It will be understood that in order to set the instrument at "danger"
the electro-magnet A of the line wire is brought into action in the
ordinary manner, when through the vibration of the bar A¹ the sema-
phore will be raised and locked in position, as described.
In operating with this instrument an audible signal will be used to
inform the man at the home station when his detent rod is dropped out
of action, and he will then in acknowledging the signal send a current
through the home circuit to withdraw the support from the semaphore.
In order to explain the action of the instruments at the opposite
ends of a section of railway, I have shewn a diagram at Fig. 4 in
which two instruments are in connection with the same line wire.
Supposing the instrument at 1 to represent the home station, and
the instrument at 2 to represent the distant station, and the signal at 1 to
have been set at "danger" by the signalman at 2, and supposing further

page_text: that the signalman at 2 has now signalled that the line is clear through
the agency of a bell apparatus, he will at the same time have caused
the rode of the instrument at 1 to drop. The vibrating lever A' will
then be in the dotted position, and the elastic strip which it carries
will, by breaking contact at g, have the effect of throwing the electro-
magnet B into circuit with the local battery. The duty of the signal-
man at 1 will now be to signal to the man at 2 that his signal is
received; this he will do by giving an audible or visible signal at 2
in any well-known manner through the line wire, at the same time
he will be required to drop the semaphore of his own instrument. In
order to make this signal and to drop his own semaphore, he will
depress the key E of his own instrument, which key is always in
metallic connection with the line wire. On the depression of the
key E he will bring the local battery into connection with the line wire
through the clectro-magnet B, and will thereby withdraw the prop from
the semaphore, and at the same time acknowledge the signal received
from the station 2.
As the working of the instrument at 2 by the signalman at 1 is
identical with that just described, no further explanation to the com-
plete understanding of the Invention will be necessary.
It will be obvious that instead of the man at the distant station
preparing for the change of position of the semaphore, he may actuate
one of a pair of arms, leaving the signal to be completed by the lowering
of the other arm by the man at the home station.
In order to prevent two opposing currents from neutralizing cach
cther and thus obstruct the action of the semaphore or other signalling
apparatus, when one line wire only is used, I provide at each station
apparatus for dividing the current on the principle of the differential
galvanometer or Wheatstone's bridge, and thus cause the unneutralized
half of the opposed currents to do the work by acting on the armature
connected with the semaphore.
Having now set forth the nature of my Invention of "Improvements
in the Mode of and Apparatus for Signalling on Railways," and
explained the manner of carrying the same into effect, I wish it to bo
understood that under the above in part recited Letters Patent I claim,
making the release of the semaphore when standing at "danger" depen-

page_text: dent upon the co-operation of the signalmen at the opposite ends of a
section of railway, in the manner and for the purpose above described.
In witness whereof, I, the said William Henry Preece, have here-
unto set my hand and seal, the Twelfth day of July, in the year
of our Lord One thousand cight hundred and seventy-three.