This document outlines the components, working, and applications of track circuits used in rail signaling. Track circuits use batteries, track relays, and adjustable resistances to detect train occupancy through changes in electrical current flow. Insulated rail joints are also used to isolate adjacent track circuits. When unoccupied, current flows through the track relay keeping it energized, but when a train is present its wheels shunt most of the current, causing the relay to deactivate. Track circuits allow signals to display red only when a track segment ahead is occupied by a train.

1. LAVIN KATIYAR
1113331094
ECE-VIIA

2. OUTLINE
 Introduction
 Components
 Working
 Do’s & Don’t
 Other technology
 Present era of technology
 Conclusion

3. INTRODUCTION
 Track circuit is simple electrical device used to detect the
Presence/Absence of train on the rails.
 Track circuit is the one of the primary input for a signal
interlocking plant.
 The signal cannot be green while there is another train on
track segment ahead.

4. COMPONENTS
 Battery.
 Track Relay.
 Adjustable resistance.
 Insulated rail joints.

5. Cond.
Battery
 Gravity cells are used .
Relay
 A relay is electrically operated switch.
 The Relay switch connections are usually labelled
common ,normally closed, normally open.

6. Cond.
 Adjustable Resistance
TRc - Track Lead Resistance at feed end
TRr - Track lead Resistance at Relay end
RT - Regulating Resistance
Rr - Rail Resistance (Rail joint Resistance)
RB - Ballast Resistance
TSR - Train Shunt Resistance
 Insulated rail joints.
 Track circuit required insulated rail joint for isolating
it the adjacent track circuit.

7. Cond.
 Nylon IRJ
 Glued IRJ
 Track circuit bonding
Rail bond need to be provided on track circuit have
point turnout them.

8. Cond.

9. WORKING
 The portion of the Track which is to be Track circuited,
is first provided with wooden or RCC sleepers and then
the rails are insulated from the rest of the Track by the
provision of Insulated rail joints.
 At one end of the Track circuit feed is connected and at
other end track relay is connected.
 When the track portion is not occupied by trains, the
fed is available for track relay and the relay is in
energized condition.

10. Cond.
When a train occupies the track circuit portion, the axel & wheels
shunt the track much of the circuit current is passed through the
wheels due to less resistive path and very less current is available
for track relay, which is not sufficient enough to pick up the relay.

11. Cond.

12. DEAD SECTION
 Those section of the track circuit in which occupation
by a vehicle cannot be detected.
 Curved track.
 Cross.
 Bridge .

13. DO’S & DON’T
 Top up distilled water if the electrolyte level is low in
batteries.
 Change the relay which is due to for overhauling.
 Replace the damaged and corroded bonding wires.
 Do not Tilt the relay.
 Do not Test the track circuit by shunting with a wire
only.
 Track circuit does not get shunted properly by vehicles.
 Its working length is dependent on immunity of track
relay.

14. OTHER TECHNOLOGY
 AC Track circuit.
 Audio Frequency Track circuit.
 Axle Counter.

15. Cond.

16. PRESENT ERA
 Indian Railways is installing a state-of-art technology
along train tracks to detect of faults and defective parts in
coaches, wagons and locomotives.
 The new system, which uses high-speed infrared and
digital cameras, will replace physical examination of the
wagons by railway staff.
 The project, which will be run as trial project will be
installed at 10 locations at an estimated cost of 73 crore
rupees in the first phase.

17. CONCLUTION
 DC Track circuit are the simplest , least costly and
most reliable type of track circuit.
 Now a days for signalling purposes , trains are
monitored automatically by means of TRACK
CIRCUIT.
 Track circuit play important role in stop accidents,
traffic .