Design Criteria of Signalling Circuits

A row of red lights (at least two) on each track circuit portion indicates the track is occupied.

When the track is not occupied, the red lights will turn off.

Provides an indication of the power source (mains, diesel, catenary).

Illuminated diagram showing track circuits in front of the first stop signal, for approach locking.

Flashing lights and audible warnings on the control panel warn of approaching trains.

A red indication on the control panel and audible warning for signal aspect/route aspect failure.

Audible warnings can be silenced with a push button, but the cancellation does not apply to subsequent failures.

Approach track circuits controlling calling-on signals are indicated separately on the diagram with a distinct symbol.

Specific requirements for designing signalling circuits, considering route setting (entry/exit based) or non-route setting (individual point operation), equipment suitability, and safety guidelines.

Design principles for electronic interlocking systems based on the type of equipment (distributed/central), interfaces, and features.

Layout and arrangement of control panel components, including the illuminated diagram, operating members, and clear distinctions between track circuits.

Detailed graphical representation of the signalling system on the control panel with operating members.

Signalling system based on the principle that routes for trains are set by entering and exiting signals.

Signalling system in which train routes are set by individually operating points.

Connections and features that allow communication and data exchange between different system components of interlocking.

Predefined or standardized circuit layouts and designs for signalling systems.

Railway installations where routes are controlled by entrance and exit push buttons.

Railway installations where route setting is done individually, allowing signal clearing by individual or group buttons/switches.

Buttons for individual operation of railway points.

Provision for point operation even during track failures; operation is recorded on a counter.

Selecting desired overlap points beyond exit signals in routes with multiple overlaps.

Selecting/setting desired alternate routes with desired overlaps.

Using distinctive colors to differentiate functions of buttons (e.g., running signal red, shunt signal yellow).

Controlling slots (e.g., for cabins, crossings) using two buttons or a switch, similar to the route-setting principle; cancellation using a common cancel button.

Crank handles are normally locked but can be released for use in point machines via a control panel.

A control panel action allowing access to point machines using crank handles, but prevent signal clearing.

The process of allowing a train to proceed through a railway signal. Crank handle release prevents it.

A key used for locking crank handles.

Equipment used to switch railway tracks.

Signal cancellation procedure for main routes, with relevant delay (home/starter).

Timing for stopping a sub-route, if needed, with specific delay.

Timer used in the event of a crank-handle release for point action failure on a route.

A visual check of relay components for defects like movement, contact wiping, arcing, pitting, dust, corrosion, cracks, or any abnormal condition

Unusual or damaged movement of the relay's armature and contact carriage.

Problem with the relay contacts failing to wipe smoothly during operation

Miniature plug-in relays should be replaced or removed after 25-30 years unless there is a failure before this time.

Wiring in equipment must align with standards, and be neatly arranged to avoid hindering other parts.

Wiring in relay cabins needs to terminate at approved terminal blocks or tag blocks.

Cable entry points near terminals should be suitably sized, positioned for convenient access, and protected from damage.

Metal-to-carbon contact miniature plug-in relays should not be overhauled, but instead replaced.

Measures ensuring safety from lightning strikes, following Section 7.

Testing and setting up of electronic interlocking systems, following parameters 19.8.5 to 19.8.12.

Regular tests for existing installations, either annually or on alteration.

SSE/JE (Signal) testing for signal circuits under 20 routes and ASTE/DSTE testing for more than 20.

Maintenance guidelines specified by the approved system maintenance manuals, with a suggested schedule.

Centralized storage of up-to-date E.I. system database files for proper operation.

Periodic verification of backup systems to ensure reliable operation.

Provides the location of the Electronic Interlocking maintenance terminal in the Signal Technician Duty room.

All interlocked level crossing gates are closed and locked when trains are present or in overlap areas.

Clearing Calling-On signals doesn't require proving track circuits in the route or overlap.

A signalling system where train routes are set by individually operating points.

Clearing shunt signals doesn't need track circuit or level crossing checks in overlap areas.

A white indication for block control is placed on control panels where the section ahead uses absolute block system and locations vary between control panel and block instruments.

Interlocking between conflicting routes is done through route interlocking electric circuits at route initiation.

Approach locking for manual stop signals is continuously active from a pre-determined point on signal approach.

Points in a route (and overlap if needed) are operated by individual switches or push buttons.

Allows point operation during track circuit failures, requiring an emergency key and verified by site traffic personnel. Operations are recorded.

A procedure for emergency operations involving verification and/or steps; prevents unintended operations.

Physical key used for controlling critical functions and operations, often required for blocking or unblocking of functions. Redudancy with multiple relays.

Allows switching between control panels or multiple control terminals (manual or password-protected), providing flexibility in operation.

Provides an indicator on the control panel/terminal to show the E.I.'s healthy status, using a blinking green LED/indicator.

Point operations are possible only when interlocking is clear and the point's track circuit is free; there are two separate relays for 'normal' or 'reverse' control.

Control terminals must be protected against unauthorized operation via physical security keys (SM Key) for redundancy.

Automatic unblocking of signals, points and lines after a predefined delay is not allowed.

Methods used to detect trains on railway tracks, including track circuits and axle counters.

DC track relays are placed in a central location and connected with dedicated cables.

Different types of axle counters include SSDAC, HA-SSDAC, and MSDAC.

Signalling cables need to meet specific requirements for the layout of the yard and availability of telephone communication in non-RE and RE areas.

Main signals use multi-unit colour light systems, shunt signals use position lights, and LEDs are used where appropriate.

Point machine control circuits require track circuit control, overload protection, and cross protection for safety.

In yards, at least two cable cores are needed for maintenance-related phone communication in non-RE zones.

Route indicators can be direction type, multi-lamp unit type, or stencil type, depending on design.

Provision of space for future additions of relays, relay groups, and racks.

Preferable fuse type for cartridge fuses, ensuring long-term reliable operation.

Grouping fuses to minimize disruption to train operations if a fuse blows.

Fuses should ideally provide a visible indication of blown status.

Precise fuse protection for each group of circuits, aiding in fast fault isolation.

Fuse arrangement that allows for straightforward replacements without impacting other circuits.

Air conditioning provision based on interlocking installation size and potential environmental factors.

Electrical department is responsible for providing and maintaining air conditioning equipment.

Testing the correct communication and data exchange between systems or components.

Verification of the logical connections and operation of control systems (like signals and tracks).

Factory Acceptance Testing; testing a system done at the manufacturer's facility.

Site Acceptance Testing; verifying system installation or repairs are functional at the location.

Having multiple power sources for electronic interlocking systems to prevent failures.

Checks the communication between multiple sub-units within the interlocking.

The wires connecting to equipment should be large enough to avoid voltage loss greater than 0.5%.

The interlocking system's control terminals need adequate redundant power supply measures.

Measures to protect electrical and electronic signalling equipment from lightning and surge damage by installing appropriate protection devices, grounding, and equi-potential bonding.

International standard outlining requirements for the design and maintenance of electrical & electronic equipment/systems for railway signalling.

Establishing reliable grounding systems for electronic interlocking units to prevent damage due to lightning or surges, including perimeter earthing, and maintaining low resistance values.

Different types of devices (Class I, II, III) used to protect signalling equipment from lightning surges at various locations (input, output, field).

Connecting different parts of a signalling system to create a common earth potential to limit voltage differences due to lightning surges, ensuring protection of equipment.

Technical specifications and guidelines issued by the Railway Board for the design, testing, and maintenance of railway signalling systems, emphasizing current standards for electronic systems.

Installation of external protective devices on buildings housing signalling equipment to safeguard against external lightning strikes.

Regular annual inspection of the ground resistance around the electronic interlocking system to ensure effective lightning and surge protection, ideally below one ohm.