Signalling systems are used to safely and efficiently control train movements on tracks. The main purposes of signalling are to provide for safe train operations, maximize track usage, and maintain safety for passengers, staff and trains. Early signalling in the 1820s-1830s involved uniformed men guiding trains by hand or flags. Signals are classified by their operating characteristics, functions, locations, and special purposes. Operating characteristics include hand, fixed, and detonating signals. Functional signals include stop/semaphore, warner, and shunting signals. Signalling has evolved from manual methods to include fixed, colour light, and other automated signals to safely direct train operations.

3. Signalling : Signalling consists of the systems,
devices and means by which trains are operated
efficiently and tracks are used to maximum extent,
maintaining the safety of the passengers, the staff
and the rolling stock.

4. NEED OF SIGNALLING
• To provide facilities for the efficient movement of
trains.
• To provide facility for safe and efficient shunting
operations.
• To provide facility for max. utility of tracks.
• To ensure safety between two or more trains
which cross or approach each other’s path.

5. HISTORY OF SIGNALLING
1825: FIRST RAILWAY LINE FOR GOODS
TRAFFIC WAS OPENED BETWEEN
DARLINGTON TO STOCKTON (U.K.)
UNIFORMED MEN ON HORSES GUIDED THE
TRAIN
1830: FIRST PASSENGER TRAIN BETWEEN
LIVERPOOL AND MANCHESTER
POLICEMAN WERE POSTED AT FIXED INTERVALS

6. CLASSIFICATION OF SIGNALS
1. OPERATING CHARACTERISTICS
2. FUNCTIONAL CHARACTERISTICS
3. LOCATIONAL CHARACTERISTICS
4. SPECIAL CHARACTERISTICS

7. OPERATION CHARACTERISTICS:
BASED ON THE WAY OF THEIR OPERATION,
SIGNALS CAN BE CLASSIFIED AS:-
Signals
Detonating Hand Fixed
Operating

8. Detonating signals:- These are placed on the rails in
foggy and cloudy weather when hand or fixed signals are not
visible. Signals explodes with a loud sound when train passes
over them.

9. Detonating signals

10. The sound of detonator draws
attention of the driver to the proximity
of the signals.
From the safety point of view, the
detonators must be placed on the rails
atleast 400 to 500m ahead of the signal
to enable the driver to stop the train, or
to obey the signals.
These signals consists of containers
with explosive and are fixed to the rails
by means of clips.

11. This type of signalling is
done manually.
Hand signals are given either by
flags fixed to a wooden handle or by
bare arms when flags are not
available during the day time.
These are generally used by guards,
station masters, cabin man or any
other authorised man
HAND SIGNAL

12. During the night time, lamps are used in which movable glass
slides of green, red and yellow sheds are provided.
Following are the signal conventions used:-
Serial no. Colours of flag/lights Meaning of signals
1 Red flag of light STOP
2 GREEN flag of light PROCEED
3 YELLOW light PROCEED CAUTIOUSLY

14. Stop or
semaphore
Warner signals Shunting
signals
Coloured-light
signals
Functional characteristics

15. STOP OR SEMAPHORE
SIGNALS
The principle of design of semaphore signals is to
show the stop position
Of any failure that happens to be in the apparatus.
The signal mechanism is so arranged that in normal
position it indicates the
Stop position.

17. Serial no. OPERATING
TIME
POSITION OF
ARM
POSITION OF
SIGNAL
INDICATION
GIVEN
1 Day time 1- horizontal
arm
2-inclined arm
45to 60 degree
“ON” position
“OFF” position
“STOP”
“PROCEED”
2 Night time 1- red light
2-green light
3-yellow light
“ON” POSITION
“OFF” position
----------
“STOP”
“PROCEED”
“PROCEED
CAUTIOUSLY”
3 Day or night
time
1-no signal
2-white
--------------
-------------------
“DANGER”
“DANGER
SIGN”

19. WARNER SIGNAL
A semaphore signal at the entrance to station
is combined with a warner signal.
The warner signal is similar to semaphore
signal in shape except a v-notch at free end.
The warner signal is placed on the same post
of semaphore signal at 1.8 to 2.1m below the
semaphore signal., which is of yellow colour.

23. Shunting signal (GROUND SIGNAL)
These signals are used for shunting
operations in stations yards and therefore ,
They are called shunting signals.
They are of the shape of a circular disc with
a red band on a white background.
The disc can revolve in a vertical plane by
pulling the lever by hand.

26. The following indications are given by
disc or shunting signals:-
1- when the red band of disc is in horizontal position
or it shows red light at night
It indicates ‘STOP’.
2- When the red band is in inclined position or shows
green light at night, it indicates
‘PROCEED’.

27. COLOUR LIGHT SIGNAL

28. SPECIAL SIGNALS
REPEATER
SIGNAL
CALLING
SIGNAL
ROUTING
SIGNAL
POINT
INDICATOR
MODIFIED LOWER QUADRANT
SEMAPHORE SIGNAL

32. REPEATER SIGNAL

33. COLOURED LIGHT SIGNALS

36. DHANYAWAD