Signaling Circuit Design Criteria

Design Criteria of Signalling Circuits

• Detailed circuit designs may be required for route setting (Entry/Exit principle) or non-route setting (individual point operations) installations, or alterations.
• Designs must meet requirements for 25 kV AC electrified areas (Chapter 22 of SEM).
• Designs adhere to approved signalling plans, control tables, control panel diagrams, and relay analyses.
• Designs accommodate specific equipment types (distributed/central electronic interlocking, MSDAC, SSDAC, UFSBI, etc.) and interfacing features.
• Use of dual OFC cables in distributed electronic interlocking is preferred for reduced copper cable extent and alternate failure paths.
• Drawings and designs follow typical templates, RDSO standards, industry best practices, and reliability, availability, maintenance, and safety guidelines.

Control Panels - General

• Illuminated diagram layouts on control panels should be well-proportioned, using domino panels for potential future expansions, and distinguished areas by color.
• Operating members (route switches, buttons, point switches, etc.) are usually shown on the illuminated diagram itself in geographical order.
• Separate diagrams for indication and operating member consoles are sometimes provided.
• Installations that aren't route-setting type allow for individual point operation.
• Route setting is based on the "Entry/Exit" principle.
• Each route has two push buttons: one at the entrance and one at the exit.

Non-route Setting Installations

• Individual push button operation clears signals, possibly with group buttons or a common switch for conflicting signals (entrance/exit).
• Separate individual push buttons or two/three position switches for control of individual points are provided,
• Route selection with alternate routes/approaches is allowed.

Control Panel Indications

• Individual point operation arrangements are provided.
• Emergency operation of points, where provided, records operations on a counter.
• Facility for slotting, cabins, crossings, and crank handles is needed.
• Cancellation of slots, with a delay, uses a cancellation button with an entrance/exit button.
• Operation recording for slots and cancellation is provided by a counter.
• 'ON'/'OFF' operated signal positions from the panel cannot be changed after the SM key is removed, though the signal can be returned to 'ON' position without altering route.
• Indication of yard and critical maintenance information is presented.
• Point positions are indicated by lights (white/yellow/green).
• Point locking indication is provided by a small white light.
• Route settings and locking are shown by white lights on sections.
• Occupied track circuits are shown by red lights.
• Power supply status indications are provided.
• Approach track circuits are indicated.
• Advance approach warnings use flashing lights or other indications with audible warnings.
• Signal lamp failures alarm by red indication and audible alert.
• Indication of aspects for the corresponding signal in the 'OFF' mode.
• Failure conditions or status of aspects are shown with flashing indications.
• Shunt signal aspects are shown by a white strip light (horizontal).
• 'A'/'AG' marker light indications are provided.

Track Circuit Indications

• Indication of occupied track circuits using a row of red lights.
• Red lights extinguish when tracks are not occupied.

Other Crucial Aspects

• Detailed signal circuit design for 25kV AC electrified areas.
• Non-use of common return wires in critical circuits.
• Limitation on number of metal-to-metal relay contacts (45 max).
• Design mandates route setting interlocking for new installations.
• Correct point settings, overlap, and isolation are critical during route setting.
• Proper clearance for slot, road traffic, and overlap is handled by signal clearance.
• Requirements for clearing Calling-On and shunt signals are noted.
• White indication is required for Block control on the last stop signal when used in Absolute Block Systems.
• Other conditions for the Non-Route setting type are mentioned in the text.
• Specific conditions for route release circuits are noted..

Additional Signal and Control Information

• Procedures, controls, and key aspects for route control, point operation, signals, and other related aspects are detailed for both route-setting and non-route-setting types of installations

Electronic Devices

• The equipment design includes features to self-detect component failures and ensure signal display of most restrictive indications.
• Safety measures are in place to handle open/short circuit conditions and variations in component values.
• Physical layout prevents external objects from causing short circuits.

Track Circuits & Axle Counters

• Standardized train detection procedures using track circuits and axle counters are followed.
• DC track relays are centrally located.
• Extensive track circuiting is done to cover the station section

Signalling Cables

• Provisions for signalling cables conform to associated standards.
• The yard requires extra cable pairs for maintenance considerations, especially during expansions.
• Earth leakage detectors are recommended.

Point Machines Operation

• Crank hand operation with distinct group wards is considered.
• Safety mechanisms and controls for point operation are considered.

Advanced Aspects of Interlocking

• Features for Advanced Starter at Junction Stations, including the automatic resetting of signals based on train passage and controlled delays, are examined
• Special considerations for level crossings, including locking and signals, are detailed.

Signal Control Circuits aspects

• Conditions for setting and locking signals in route-setting, as well as non-route-setting installations, are explained.
• Consideration of procedures for clearing signals when conditions meet the requirements for specific types of signals are noted.
• Instructions on handling and restoring signals in emergency situations are provided to ensure safety

This quiz covers the essential design criteria for signaling circuits, focusing on requirements for various electrified areas and the integration of specific equipment types. It also highlights the importance of adhering to approved plans and best practices in the field. Prepare to test your knowledge on circuit designs, control panels, and industry standards.