MEDHA’s Electronic Interlocking System MEI 633 is a fail-safe, state-of-the-art Distributed Interlocking System. The System has been designed to CENELEC Standards to meet SIL-4 safety specification. It is based on two out of two architecture with a hot standby provision and automatic change-over facility. The System provides all the Interlocking features including Route Setting, Route Release, Point Operation, Track Occupancy Monitoring, Overlap Protection, Crank Handle Operation, Level Crossing Gate Interlocking, and provision for Block working.

The Central Interlocking Unit (CIU) uses Two out of Two Architecture with two independent channels computing the Vital Interlocking Logic and a Supervisory Processor monitoring the two Vital computing channels. Hot standby with automatic change-over facility is provided. Redundant communication channels to Object Controller (OC) and Panel Processor (PP) are provided through two Communication Processors. OFC interface with Ring configuration is used for communication between CIU and OC, CIU and PP. Independent Power Supplies are provided for each Processo module for maximizing availability.

Object Controllers (OC) control the field gear through Fail-safe Signaling Relays. One CIU can be connected to a maximum of 32 OCs. Each OC is capable of handling 24 Vital Outputs and 40 Vital Inputs. Two Communication Modules are included in each OC to provide redundant communication channel with CIU. Each OC consists of 8 Wayside Function Modules (WFMs), with each WFM capable of handling 8 Inputs or 8 Outputs. Each WFM is further based on two out of two architecture with two independent channels handling each Vital I/O. Redundant Power supplies are provided for WFMs for maximum availability.

Panel Processor provides the Interface between the Operator’s Control Cum Indication Panel and the CIU. Redundant Processors with Independent Power Supplies are provided for maximum availability. System can be controlled either by Operator Control Panel or Visual Display Unit (LCD Display) based Control Terminal through software.

A Windows based user friendly, graphical Application Generation Tool Suite with high level of automation is provided for generation of Yard specific Application Data. The Tool Suite also provides the facility for Reverse Compilation and Relay Diagram Generation for easy verification of Application Data.

The Maintenance Terminal provides the Diagnostic Interface through Online and Off-line Event & Fault and Yard Status Display with Date and Time Stamp. The Maintenance Terminal records all the Events and Faults. The recorded events can be replayed to view the Yard Status at any given time.