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.