1. Unit 3- Signalling and Interlocking
Objective-
To provide facilities for the maximum utility of
the track with safety as the prime concern.
2. Classification of Signals
1. Based on operational characteristics
• Detonating (during foggy or cloudy weather
where other signals are visible)
• Hand (flags/ lamps)
• Fixed
2. Based on Functional characteristics
• Stop/Semaphore
• Warner (1st signal for a station)
• Shunting (disc/ground)
• Coloured
5. Classification of Signals
3. Based on Locational characteristics
• Reception (outer (1st stop signal)/home)
• Departure (starter(last stop signal)/advance starter (if provided
becomes last stop signal)
4. Based on Special characteristics
• Repeater (co-acting, when driver’s vision is obstructed by like
overbridge)
• Routing
• Point indicators
• Calling on signals (to proceed cautiously during repair works)
Sequence of signals: warner(1st)-outer-home-starter-advance
starter (last).
Block section- distance between last and 1st stop signal.
8. Types Control Systems
1. Absolute block / space interval/lock and
block system (telephonic conversation
between controller of control room and
station masters of block stations to issue
tokens as authority to enter block sections)
9. Types of Control Systems
2. Centralised traffic control system
(centralization of operations using illuminated
track diagrams)
10. Types Control Systems
3.Automatic train control system (electric track
circuiting which alarms the driver through a
siren for any danger)
11. Interlocking of tracks
Principles-
To set and lock the points and signals properly for an
approaching train against the feasibility of conflicting
movements i.e route should be clear of any
obstructions for that particular train movement.
14. • Mechanical/ electrical consists of
1. Stretcher bar
2. Treadle bar
3. Lock bar and tappet arrangements
4. Connecting devices (rods, cranks, etc)
5. Temperature compensators
16. Included parameters
• LWR (long welded rails)/CWR (continuously welded rails)– this
actually reduces number of joints which eventually increases
service life of rails as less defects and failures will be there
then)
• Diesel and electric traction
• Wider , correct and uniform gauge
• Proper alignment and high sleeper density
• Automation in train control operation through efficient
signaling (in-cab signaling where track and train communicate
to each other)
• Better suspension of rolling stock (vehicles over railway track)
• Modified locomotives and coaches
• Dynamic forces and fencing to tracks
17. Track tolerances
• Service tolerances (gauge variations on
straight vis a vis curve track, alignment
variations, uneven-ness, etc.)
• Safety tolerances
• Speed restrictions
• Loading and construction gauge (Loading
gauge+ some clearance to pass through
tunnels and under bridges)
