The document discusses railway signalling systems. It describes how signals are used to safely regulate train movements and maximize track utilization. Early systems used policemen and hand signals, while modern signalling was introduced in England in 1842 using fixed semaphore signals and detonators. Signals communicate different instructions like stop, caution, or proceed using aspects like colored lights, positions of arms, or detonator explosions. The classification, types, and locations of various signals are also outlined.

2.  The purpose of signal is primarily to control and
regulate the movement of trains safely and
efficiently.
 It includes use and working of signals, points,
block instruments, and other allied equipments
in a predetermined manner of safe and efficient
running of trains.
 It enables the movement of trains to be
controlled in such a way that existing tracks are
utilized to the maximum.

3. The history of signalling goes back to the
olden days the two policemen on horse back
were sent ahead of the train to ensure that
the tracks were clear and to regulate the
movement of trains.
In later years, policemen in uniform
placed at regular intervals to regulate the
movement of trains.
Railway signalling in its present form was
introduced for the first time in England in
1842.

4. In railway terminology “It is a
medium of communication between
the station master or the controller
sitting in a remote place in the
office and the driver of the train”

5.  To regulate the movement of train so that
they run safely at maximum permissible
speed.
 To maintain a safe distance between trains
that are running in the same line in the same
direction.
 To ensure the safety of two or more trains
that have to cross or approach each other.
 To provide facilities for safe and efficient
shunting.

6.  To regulate the arrival and departure of
trains from the station yard.
 To guide the trains to run at restricted speed
during the maintenance and repair of tracks.
 To ensure the safety of train when it comes
in contact with road traffics at level
crossings.

7. Characteristics Basis of classification Examples
Operational Communication of
message in audible and
visual form
Audible: Detonators.
Visual: Hand signals (or)
fixed signals
Functional Signalling the driver to
stop, move cautiously,
proceed or carry out
shunting operations
Stop signals,
Shunt signals,
Speed indicators.
Location Reception or departure
signals
Outer, home, starter
and advanced starter
signals.
Special
characteristics
Meant for special
purposes
Calling-on signals,
Repeater signals,
Speed indicators, etc.

8. signal
Audible
(detonator)
visible
Hand signals Fixed signals
Caution indicator Stop signals
coloured light
(2, 3 & 4
aspects)
Distant, home, starter,
advanced starter calling
on, shunt repeater,
automatic
Semphore signal
(2, 3 & 4 aspects)
warner, outer, home starter,
Advanced starter, calling-on,
Shunt, repeater, coaching.

9. Classification of
station
Minimum required of
signals
Remarks
A class Warner, home and
starter
An outer signal can be provided
after obtaining special
permission.
B class Outer and home In multiple-aspect upper
quadrant (MAUQ) areas, distant
home and outer signals are
provided.
C class Warner and home In MAUQ areas, the warner
signal is replaced by distant
signal.

10.  Audible signals such as detonators and fog
signals are used in cloudy and foggy weather
when hand or fixed signals are not visible.
 Detonators contain explosive materials and
are fixed to rail by means of clips.
 Its kept 90m ahead of signal to indicate the
presence of signal to the driver.
 Once the train passes over the detonators
thereby causing them to explode, the driver
becomes alert and keeps a lookout for the
signal.

12.  These signals are in the form of flags (red and
green) fixed to wooden handles that are held by
railway personal assigned this particular duty.
 In the night, hand lamp with moveable green and
red slides are used.

13. These are firmly fixed on the ground by the
side of the track. And its further subdivided into
two types,
 Caution indicator
 Stop signals
These are fixed signal provide for
communicating the track ahead is not
fit for the running the train at normal
speed.
These signals are used when
engineering works are underway and
are shifted to one place to another
depending upon requirement.

14. No Type of signal Indication Location
1 Outer signal Entry of train into station
limits. The driver must bring
the train to 9m fro the signal.
Beyond the
station limit,
about 580m from
home signal
2 Home signal Train must come to a halt short
of the signal.
At about 180m
short of points
and crossings.
3 Routing signal Route earmarked for the
reception of the train.
Signal for the
main line at the
higher level than
that for the loop
line.
4 Starter signal Limit up to which a particular
line can be occupied without
infringing other line.
At departure
point.
5 Advance starter
signal
Marks that end of limit. About 180m
beyond trailing
time.

16.  The word “SEMAPHORE” was first used by a Greek
historian. ‘sima’ means sign and ‘phor’ means to
bear.
 It consist of a moveable arm pivoted to a vertical
post through a horizontal pin.
 The semaphore signal can be used as ‘stop signal’
as well as warner signal.
 These signals are operated by hand levers or
bottom located in a central cabin, which is
normally provided nearer the station master’s
office.
Position of
signal
Position of arm Colour during
night
Indication
On Horizontal Red Stop or danger
Off Inclined 45º to 60º
below horizontal
Green Proceed or line
clear

18.  The warner signal is similar to semaphore
signal in shape except V-notch at free end.
 Warner signal is a signal in advance of stop
signal. The most restrictive aspect of a
permissive or warner signal is driver can pass
the signal even when it is at ON position.
 The warner signal is placed on the same post
of semaphore signal at 1.8m to 2.1m below
of semaphore signal.
 The warner signal is painted yellow and
exhibits yellow or amber colour at night
instead of red.

20.  In this system, drivers perceive the signal
through coloured lights.
 Special lenses and hoods protect these light.
Therefore, drivers can directly see the colour
lights even under brightest sunlight.
 The following are the types of colour light
signals:
 Two aspects (green and red)
 Three aspects (green, yellow and red)
 Four aspects (green, double yellow, yellow
and red)

21. No. Colour of signal Indications
1. Red Stop dead.
2. Yellow Proceed cautiously but be prepared to stop
at next signal.
3. Double yellow Proceed at full speed, but be prepared to
pass cautiously at next signal.
4. Green Proceed confidently.