JD-1A Computer Interlocking System, which adopts advanced computer technology, bus technology and network technology, realizes a station interlocking system features high reliability, fail-safe, perfect functions and easy operating and maintaining performance. The system reserves the 6502 electric centralized executing circuits, including all the matured relay circuit of switch startup circuit, lighting circuit of signaling machine, track circuit and contacting circuits etc. The other circuits are replaced by the computer interlocking system. The key parts of the computer interlocking system adopt redundancy hot standby to ensure the uninterruptible operation in case of fails. The maintenance machine of the system monitors real-timely the operation of the station and interlocking system, records the operation of the watchers and the system faults and the reasons thereof, which will provide help for the accident analysis and maintenance to the system.¡¡