SOLID STATE INTERLOCKING SAFEGUARDS JAPANESE COMMUTERS
Katsuji Akita · Railway gazette international · 1985
Japanese National Railways (JNR) has introduced a solid-state interlocking system known as SMILE (Safe Multiprocessor for InterLocking Equipment). Located on a high-density suburban line, this installation must be very reliable because any interruption would cause serious delays. Biggest challenge in development of SMILE was design of a fail-safe, fault-tolerant system using a general purpose computer. Tests and a prototype installation gave JNR experience for designing the multi-microprocessor interlocking that went in at a junction between Yokahama and Tokoyo traversed by 700 trains daily. Information on control and signal indications is exchanged automatically between SMILE and the existing Automatic Train Control (ATC) system. SMILE is claimed to have built-in functions that make it superior to relay interlocking in terms of operation, maintenance, economy and flexibility in choice of functions.