Railway Signalling and Telecommunication Quiz

Study Notes

A sighting board is an indication to the driver that they are approaching the first stop signal of a railway station.
The function of a sighting board is to allow the driver to estimate the location of the next stop signal from the current location so that they can start applying brakes in case the first stop signal is in an 'on' position.

Stop Signal: indicates the entry of a train from a block section into the station limits.
Outer Signal: the first stop signal at a station, provided at an adequate distance beyond the station limits.
- Has one arm but has a warner signal nearly 2 m below on the same post.
- When the outer signal is in the 'on' (or stop) position, it indicates that the driver must bring the train to a stop at a distance of about 9 m from the signal and then proceed with caution towards the home signal.
Home Signal: provided about 190 m short of the points and crossings.
- Arms provided on a home signal are generally as many as the number of reception lines in the station yard.
- When a home signal is in the 'on' (or stop) position, it indicates that the train must come to a halt short of the signal.
Routing Signal: indicates the route that has been earmarked for the reception of the train.
- Fixed on the same vertical post for both main and branch lines.
- The signal for the main line is kept at a higher level than that for the loop line.
Starter Signal: a stop signal that marks the limit up to which a particular line can be occupied without infringing on other lines.
- Provided for each line and controls the movement of the train when it departs from the station.
Advanced Starter Signal: the last stop signal provided for the departure of trains from a station.
- Provided about 180 m beyond the outermost points or switches and marks the end of the station limits.

Classified into two main categories: Mechanical signalling system and Electrical signalling system.
Solid-state signalling system is also in use.
Each system of signalling comprises:
- Operated units such as signals and points.
- A transmission system such as single- or double-wire transmission or electrical transmission.
- Operating units such as levers and press buttons.
- Monitoring units such as detectors, treadle bars, and track circuiting.

Relies on physical mechanisms to convey signals to train drivers, typically through the use of levers, wires, rods, and semaphore arms.
Uses semaphore signals, which are operated by means of either a lower quadrant or an upper quadrant signalling system.
Lower quadrant signalling:
- The semaphore arm of the signal can only take two positions, namely, horizontal or lowered.
- Not possible to include a third position for the semaphore arm, such as vertically downward position.
Upper quadrant signalling:
- Can display more than two aspects.
- Possible to incorporate three positions of the semaphore arm, namely, horizontal, inclined at an angle of about 45° above the horizontal level, and vertical.

A device or system meant to ensure the safety of trains by eliminating human error.
Ensures that the points and signals are set in such a way that the cabin man cannot lower the signal for the reception of a train unless the corresponding points have been set and locked.
Can be defined as an arrangement of signals, points, and other apparatus so interconnected by means of mechanical or electrical locking that they can be operated in a predetermined sequence to ensure that there is no conflicting movement of signals and points and trains run safely.
Methods of interlocking:
- Key interlocking: the simplest method of interlocking, still exists on branch lines of small stations on Indian Railways.
- Mechanical interlocking: an improved form of interlocking, provides greater safety and requires less manpower for its operation.