| Have you ever been in a
busy signal-box by night, the windows of which
command a view over, perhaps, two or three acres
square of railway lines, with a vast number of
mutable lights, varying in hues of red, white,
and green? It is a charming sight.
But one which I must ask the reader not to
entertain any sanguine hopes of witnessing from
this point, as all signal-boxes are necessarily
kept strictly private, in order not to divert the
attention or confuse the mind of the signalman.
From
here locomotives and vehicles can be seen moving
about in all directions in various parts of the
yard. Now a passenger train, guided by the
symbolical lights along the line, is rushing
through at the rate of 40 or 50 miles an hour.
Its course through the yard is quickly filled by
a goods train from the adjoining line. Now an
express is hurrying through in the opposite
direction, leaving in its trail a long column of
smoke and steam. The goods recrosses, and in a
few minutes more is following in the wake of the
express.
The
exterior workings, as seen from the signal-box
windows, tend to confuse rather than enlighten
the onlooker, and might reasonably cause him to
wonder how these are effected with such
marvellous facility and a minimum of accidents.
To
know this, a description of the signalbox, with
its working, is necessary, for it is here the
secrets lie, and herein the running of the trains
is regulated.
The
first object in the box that meets the eye is a
long row of, perhaps, 50 or 60 levers, the top
parts of which are brightly polished, while the
bottom parts (about two-thirds) are painted in
various colours, indicative to what they apply.
For instance, black denotes that all levers
painted in this colour work the switches which
turn the engines from one line to another; red,
danger signals; blue, safety locking-bars; and so
on. In addition to this, there is a brass plate,
on which the use of the lever is inscribed, and
another, upon which is inscribed the consecutive
number of the lever, attached to each lever.
There is also a diagram of all the switches and
points and signals, with instructions for
working, hung up in a conspicuous position in the
box.
But
how is it that the signalman, who is continually
pushing and pulling the levers, never pulls the
wrong one, thereby throwing the train off the
line, or turning it out of its course? This is a
question often asked, most people being under the
impression that all the levers can be pulled at
any time and anyhow.
Happily
this is a fallacy which may be got rid of by a
brief explanation of a kind of mechanism known as
interlocking. This interlocking gear is generally
in the bottom storey of the box, immediately
beneath the lever-frame, and invisible from the
box. It varies in construction according to the
different manufacturers. It consists generally of
a lot of notched iron rods being crossed with
others working conjointly with the levers above.
They are arranged so that when a signal is pulled
off for a train to pass, the lever that works it
also works the locking gear underneath in a way
that all other levers applying to switches on the
same line are locked. Hence it is impossible to
move a pair of switches when the signals are off
for a train to pass.
On the
other hand, no signals can be pulled unless the
road is set right, and the switch levers properly
secured in their normal position. So intricate is
this system of interlocking that, even if a
switch-lever is not properly put back and
securely fastened in its slot, the signal-levers
cannot be pulled. In short, the interlocking
system may be justly termed the grandest thing in
connection with railway signalling.
Next
in order comes the block-telegraph system of
signalling. All signal-boxes are furnished with
telegraph instruments and bells to signal from
box to box for each line of rails; but the system
under which these are worked, and the mode of
indicating the description of trains, would fill
a volume. Therefore, let a few principal facts
suffice.
A, B,
and C represent; three consecutive signal-boxes,
and the process of signalling a train is as
follows :
When a
train is ready to leave the starting-point, A.
the signalman, by means of the electric bell,
calls the attention of B, and then gives the
prescribed, "Is line clear?"' bell and
instrument signals. If the line be clear, these
signals are repeated back to A, and the needle of
the instrument fixed to " Line clear."
The signalman at A then pulls off his signals for
the train to proceed, and, when it leaves, gives
the " Train entering section " signals
to B.
B then
turns the needle of the instrument to "Train
on line," in which position it is kept until
the train passes B, and is travelling at its
usual rate of speed, with tail-lamps on. These
show that the train is complete, and that no part
has become detached.
Being
thus assured all is well, the signalman at B
gives bach to A the " Train out of section
" signal, and places the needle of his
instrument in its usual position - vertical. Each
signalman asks, " Line clear?" to the
box in advance when the train leaves the box in
the rear. In this way the trains are signalled
throughout the line. By the strict observance of
these rules, which are rigorously, enforced, it
is absolutely impossible to have two trains in
the same section at the same time.
Another
thing which often puzzles the public is how the
engine-driver picks out his signals and speeds
along through the stations and yards with such
confidence in those guiding lights. A few words
on the subject may, perhaps, be acceptable. The
ingress and egress of stations is controlled
generally by four signals — namely, "
Distant," " Home," "
Starting," and " Advance
starting." The driver sights the "
Distant " first — it is distinguished
from the others by' the outer end of the arm
being swallow-tailed in shape. It is the only
signal that may be passed when at danger. Should
this signal be at danger, the driver reduces
speed, and proceeds cautiously to the next, being
prepared to stop if necessary. Should it be off
it indicates to the driver that all the others
are off also, for, by the interlocking just
explained, this signal cannot be pulled before
all the others are pulled. Hence the speed
through stations. The " Home " signal
controls the entrance into the station; the
"Starting" signal and "Advance
starting" signal control the departure into
the section ahead for the next station.
Signals,
as a rule, are so placed as to indicate by their
positions the line's to which they apply,
generally as follows: The first, or top, arm to
the line on the left; the second arm to the line
next in order from the left; and so on.
Otago
Witness, Issue 2387, 30 November 1899, Page 62
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