IMPROVEMENTS IN SIGNALLING ON RAILWAYS AND APPARATUS THEREFOR."
Year: 1880

page_text: PROVISIONAL SPECIFICATION left by William Thomas Cassel Pratt at the
Office of the Commissioners of Patents on the 20th May 1880.
WILLIAM THOMAS CASSEL PRATT, of Newport, in the County of Monmouth.
"IMPROVEMENTS IN SIGNALLING ON RAILWAYS AND APPARATUS THEREFOR."
This Invention relates to improvements in signalling on railways and apparatus
therefor, whereby the whole of the permanent way and rolling stock are under the
complete control of the signalman or signalinen employed to signal trains from one
box to another, so that in the event of any train breaking down, leaving the
metals, or running across both the up and down lines (in the case of double lines),
the fact of the train leaving the metals is instantly and automatically communi-
cated to the signalman without the aid of either the driver or the guards of the
said train, whereupon the signalman would immediately block the other line, that
is to say, either the up or down line, as the case may be, and would thus prevent
any train coming in collision with the wreckage on the permanent way.
This blocking of the other line is effected by communicating with the engine
driver of any train which may be approaching the scene of disaster.
In carrying out my Invention I make use of an electrical circuit composed of
two line wires, as ordinarily used in telegraphy (galvanised), running between the
metals, and guaged a certain distance from and above the same (the two wires
being required for each line), as each line must have a separate circuit. Theso
wires are supported by suitable stays from the centres of the sleepers, and are
separated a fixed distance from one another throughout their entire length. The
said wires extend between two signal boxes or stations, as may be required, and
within the signal box which any train may be approaching is placed a battery in
circuit with the wires connected with that particular line of metals which the train
is upon.
Every train approaches the battery, and as the engine forms part of the circuit
anything, or another engine coming behind the first engine, cannot enter into the
same circuit, as the first engine short-circuits the battery current, and so releases
the bell or indicator on the train in the rear, consequently stopping it. The box
at the end of an electrical circuit is supplied with a switch and bell or other
suitable indicator, so that if the circuit be broken anywhere between the two boxes
(or in them by means of the switches) the bells or indicators are released in the
same, and also on the engine or break van of any approaching train on those

page_text: particular electrical circuits. Each engine and break van is fitted with sets of
steel rollers playing on the two wires, and by means of a spring adjustment are
kept constantly in connection with the wires, and thus the circuit is closed when
the rollers are on the wires (and the switches are shut also); consequently if the
rollers leave the wires, the circuit being broken, communication is at once made
with both signalmen. Again, if either signalman knows of a danger he opens his
switch or switches according to requirements, and thus stops the train approaching
that danger.
From the preceding description it will be understood that upon any train leaving
the metals the fact is instantly and automatically communicated to the signalmen,
as the circuit is broken. Also if any wire should break from the effects of strain,
or any kind of accident occur, it would also be communicated to the signalmen.
Further, any driver can raise one set of rollers from one of the wires, and thus
break the circuit in case of any kind of break down or obstruction.