Signalling Circuits Design Criteria

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Questions and Answers

What color indicates that a stop signal is at 'ON' on the control panel?

Red light.

What should be indicated on the control panel if the permissive signal is 'ON'?

A yellow light.

How is a stop/permissive signal indicated as 'OFF' on the control panel?

By a green, yellow, or double yellow light.

What does a flashing indication signify when the signal 'OFF' aspect fails to light at site?

It indicates the corresponding signal aspect on the control panel. Signup and view all the answers

What color light is used for the 'ON' aspect of a shunt signal on an independent post?

A white light strip or two miniature white lights. Signup and view all the answers

What indicates the 'OFF' aspect of a shunt signal below a running signal?

A slanting white light strip or two miniature slanting white lights. Signup and view all the answers

What should be lit on the control panel for 'A'/'AG' marker indication during automatic working?

A white light. Signup and view all the answers

What is the indication for 'OFF' when a 'Calling on' signal is active?

A white light is lit below the running signal indication. Signup and view all the answers

What does the Yellow Steady indication on the control panel signify?

It signifies that the CH key is in and locked. Signup and view all the answers

What is indicated by a Red Flashing light on the control panel?

It indicates that the CH key is released but not extracted, or it has been inserted back without taking control. Signup and view all the answers

What happens after a two-minute timer when an emergency route cancellation is initiated?

The white light indication for signal lock will extinguish. Signup and view all the answers

What does the Yellow Flashing indication represent when the gate slot is released?

It represents that the gate is not yet open or the slot has not been taken back. Signup and view all the answers

How does a Red Steady indication alert the operator regarding the gate's status?

It signifies that the gate is open. Signup and view all the answers

What is the purpose of using a buzzer in conjunction with push buttons on the control panel?

It alerts the operator that a push button has been left pressed. Signup and view all the answers

What types of light sources may be used for control panel indication lamps?

They can be operated by 24V miniature type bulbs or light-emitting diodes (LEDs). Signup and view all the answers

What design consideration must be taken into account for return wires from indication lamps and relays?

They must be suitably bifurcated to prevent damage from excessive current. Signup and view all the answers

What must be ensured for interlocked level crossing gates before allowing road traffic?

They must be closed and locked against road traffic, with proof of signal clearance in the route and overlap. Signup and view all the answers

What is not required for the clearing of Calling On signals?

Proving of track circuits in the route and overlap is not required. Signup and view all the answers

What kind of locking should be provided for manual stop signals?

Approach locking or dead approach locking should be provided for all manual stop signals. Signup and view all the answers

Describe the purpose of interlocking between conflicting routes.

It achieves safety by using route interlocking electric circuits at route initiation stages. Signup and view all the answers

In what situation is a white indication for block control on the last stop signal necessary?

When the section ahead is worked on an Absolute Block System and the control panel is placed at a different location. Signup and view all the answers

What should be clear in the route before clearing shunt signals?

Proving of berthing track circuits, points, and LC gates in overlap must be clear. Signup and view all the answers

State the requirement for track circuits in the route before interlocked level crossings.

The track circuits in the route up to the next signal or dead end must be clear. Signup and view all the answers

What conditions must be met for route setting and clearance of signals?

Points in the selected route need to be operated to the required position by switches or group push buttons. Signup and view all the answers

What are the two conditions required for a control switch to clear a signal?

The SM's key must be in, and the interlocking must be free. Signup and view all the answers

When does complete route release become effective?

Complete route release is effective only after the signal governing the route is put back to 'ON' and the corresponding route switch/button has been operated. Signup and view all the answers

How does the route release circuit ensure safety concerning multiple track sections?

The circuit is designed so that a route section does not release just by picking up the concerned track relay; it requires the next track circuit to drop and pick up. Signup and view all the answers

What role does time delay play in route release for single track circuits?

In single track circuits, route release is controlled after a predetermined time delay. Signup and view all the answers

Why is sectional route release necessary in installations with more than 100 routes?

Sectional route release allows for managing multiple routes effectively and safely by permitting the setting up of other routes if interlocking allows. Signup and view all the answers

What happens in installations with non-route setting systems regarding sectional route releases?

In non-route setting systems, sectional route release is provided if routes exceed 100, and complete route release requires the signal to be put back to 'ON'. Signup and view all the answers

What is the requirement for automatic route release in systems with sequence proving relays?

Automatic route release is provided when sequence proving relays are used to prove the authorized passage of a train. Signup and view all the answers

What is the significance of detecting and locking points in the operation of railway routes?

Detecting and locking points are crucial for ensuring that all routes, including overlaps, are set and secured before a train passes. Signup and view all the answers

What conditions must be met to release a route in an emergency after the signal has been put back to danger?

The train must not have passed the signal during the time interval. Signup and view all the answers

How should the overlap points behave when the route is released by the passage of a train?

Overlap points shall be released only after a suitable time delay following the clearance of the last point track circuit. Signup and view all the answers

What is required for the cancellation of an emergency route or sub-route?

Cancellation must be operated after physical verification of the line by a traffic representative. Signup and view all the answers

What should happen if a signal is not able to assume an 'OFF' aspect in installations with route setting facilities?

The relevant route switches/buttons must have been operated and the route correctly set and locked. Signup and view all the answers

In a system with non-route setting facilities, what conditions must be met for a signal to assume an 'OFF' aspect?

The route must be set and locked, relevant track circuits must be clear, and the signal switch/button must be operated. Signup and view all the answers

What happens when any part of a circuit related to signal control fails?

The failure will cause the signal to display the most restrictive aspect. Signup and view all the answers

What is required for self-restoring type push buttons to allow a signal to assume an 'OFF' aspect?

The concerned push buttons must be pressed simultaneously for 3 seconds and then released. Signup and view all the answers

What procedure should be followed to ensure record-keeping for emergency route cancellations?

Every cancellation must be recorded on a non-resettable counter and in a register maintained by the traffic representative. Signup and view all the answers

What happens when there is a failure of the main signal aspect lighting?

The more restrictive aspect lights automatically. Signup and view all the answers

Why is fouling protection and approach locking important in signaling systems?

They help prevent accidents by ensuring that trains do not enter conflicting routes. Signup and view all the answers

What is required for a starter signal to be released at junction stations?

It must be released by an advance starter signal. Signup and view all the answers

What does the automatic replacement of signals to 'ON' after a train passes signify?

It indicates that the signal system is reset for the next train movement. Signup and view all the answers

What condition must be met before a main signal can assume the 'OFF' position?

All interlocked level crossing gates in its route must be closed and locked against road traffic. Signup and view all the answers

Explain the locking mechanism for interlocked gates at stations.

Gates cannot be opened until the concerned signal is set to 'ON' and the route to the gate is proved clear. Signup and view all the answers

Describe how locking of advanced starter and starter signal works at junction stations.

It's required at diverging ends and twin single line block working stations, ensuring safe train routing. Signup and view all the answers

What role do point control relays play before a signal shows 'OFF' aspect?

They must be proved to ensure the correct routing of trains. Signup and view all the answers

Study Notes

Design Criteria of Signalling Circuits

Detailed designs for interlocking circuits may be needed for route setting (entry/exit) or non-route setting (individual point operation).
Designs must meet RE (relay) stipulations in 25KV AC electrified areas, as per Chapter 22.
Designs must adhere to approved signalling plans, control tables, control panel diagrams, and relay analysis.
Designs should fit specific equipment (e.g., distributed/centralized electronic interlocking, MSDAC, SSDAC, UFSBI).
Use of dual OFC cable is preferred in distributed electronic interlocking to reduce copper cable extent and offer alternative paths.
Designs should meet typical templates, standards (e.g., RDSO), guidelines, industry best practices, and principles of reliability, availability, maintenance, and safety.

Control Panels

Illuminated diagrams on control panels should be well-proportioned and use different colours to distinguish track circuit areas.
Domino-style panels should be used for additional facilities.
Operating members (e.g., route switches, point switches) should be shown on illuminated diagrams in geographical order.
Separate illuminated diagrams and consoles may also be provided.
Route setting is based on the "Entry/Exit" principle. Route setting type installations use two push buttons (one at the entrance and one at the exit).
Non-route setting installations allow individual operation of points.

Non-Route Setting Installations

Individual push buttons can be used to clear a signal following point actuation.
Multiple overlap routes allow selection and setting of desired overlaps.
Separate pushbuttons for route operation at entrance and exit.

Control Panel Indications

Provisions for individual point operation.
Counter for emergency point operation.
Slotting for adjoining cabins.
Route cancellation using a group button along with entrance/exit buttons.
Signal indication of the last operated position cannot be changed when removing power to the system.
System indicators to show yard position for maintenance personnel.

Point Indications

Point positions indicated by white/yellow/green lights, near point switches, and white strip lights on the point zone(pushbutton).
Flashing display shows setting operations.
Point-locked indication by a small white light.

Route Indications

Route settings and locking indicated by white lights (at least two) on each track section.
Route indicating lights are extinguished when route not set.
Entire route lit by white lights when correctly set.
Lighting may change to red and back to white when train passes on the route.

Signal Indications

Stop signal indicated by red light.
Permissive indicated by yellow.
Signal 'OFF' normally shown by green or yellow/double yellow lights (flashing in case of failure).
Indication of 'ON' aspect for shunt signals on a separate post is by white light strip.

Track Circuit Indications

Occupied track circuits indicated by red lights.
Lights extinguished when track not occupied.

Power Supply Indications

Availability indicated, e.g., from Mains/Diesel Generator/Catenary 1 or 2.

Other Indications

Approach track circuits displayed on the illuminated diagram.
Advance approach warnings (flashing lights/ audible warnings).
Signal cancellation by pressing a button.

Route Setting Type

Interlocking, point setting, and signal clearance follow specific conditions.
Locking of points in correct route position is essential.
Level crossings, isolations, and fouling clearances must be validated.

Non Route Setting Type

Point operations use switches and/or pushbuttons for route selection.
Entrance/exit buttons are used for clearing signals.
Point operations need track circuitry checks.

Route Release Circuits

Route release circuits must be designed for sequential track circuit drop-and-pickup.
Installations with route setting can release sections if more than 100 routes.
Non-route setting installations require signal 'ON' before release.
Sectional release is available for cases of more than 100 routes.

Signal Control Circuits

Signals will only turn 'OFF' if relevant routes have been set and locked, and track circuits are clear ('OFF' aspect not possible otherwise).
Emergency operations (with counter recording) are possible for point/route failures.
Cross-connections and short circuits are prevented.

Point Control Circuits

Points stay in last set position or may be automatically reset after train passage.
Point operations possible while interlocking is free and relevant track circuits are clear.
Emergency point operation is also available.
Interlocking should be minimal.
Improper operation (e.g., cross-connection) prevention.

Crank Handle & Siding Control Keys

Crank handles allow manual point operation (interlocked with signals).
Point control mechanisms have failure provisions.

Cross Protection Features

Internal circuits can skip cross-protection if not required.
External circuits need protection against cross connections and interference.

Control Panel/Control Terminal

Control panels must use appropriate size displays (showing layouts and features).
Redundancy/redundant designs (e.g. control display modes) are needed.
Video display units needed where necessary(e.g., layout display).
Indications on terminals must conform to those used on other equipment.

Signalling Cables

Use of at least two cable cores and/or separate cables for maintenance operations.

Signals in Outdoor

Main signals are multi-color light type.
Route indicators are available (direction, multi-lamp, stencil types).
Marker lights for semi-automatic signals are used.

Point Machines

Point control circuits for protection
Using crank handles for operation.

Precautions

Design of components should avoid failure.
Circuit designs should ensure failsafe operations.
Maintenance is required for electronic components.

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Description

This quiz focuses on the design criteria for signalling circuits, including important regulations and best practices for interlocking circuits. It covers key aspects such as requirements for relay stipulations, control panels, and adherence to industry standards and templates. Test your knowledge on the critical elements that ensure reliability and safety in signalling designs.