The invention is especially related to guiding against error operation of microcomputer applicable to preventing error operation to plant and station for power distribution and delivery. Electromagnetic lock in numeric code in use for guiding against error closedown includes parts: upper cover, base, dead bolt, guide sleeve, lock nut, spring, director element in the upper cover, as well as rack for mounting electric magnet, magnet inside the rack, and circuit control board installed inside the lower cover. The guide sleeve is fixed on upper part of the dead bolt. Being corresponding to position of the director element, V type slot is on outside the guide sleeve. There are two dry reed tubes on the circuit control board, and there are magnets on outside the guide sleeve located at places corresponding to positions of the tubes. The invention is applicable to wired distributed type microcomputer system for guiding against error closedown. Features are: raised real time and reliability.