Redundant control method and apparatus for fail safe computers

Control procedure of a treatment system that requires a security for a transport comprising at least two computers (10, 20) each arranged secure outputs which can be in a restrictive state or a permissive state, restrictive state is a state of intrinsically safe character, such computers can exchange information between them, each intrinsically safe computer is able to one calculation program to define output states (SA), a computer is master and the other is slave where the two computers are provided with safety means to detect their own malfunction, and in which, in case of detection of failures in the master computer, the master computer becomes slave, this procedure consists of: a) operation in redundant mode in which each of the computers calculates (202, 212) output states, characterized by the following steps: - receiving (203, 213) output states (SA) determined by the other computer - comparison (204, 214), for each output states determined by the two computers, - detection of a state of divergent operation, if the two computers have determined two different states for the same secure output - if a divergence is detected for at least one secure output, determining (206) the state of said divergent output keeps a transition from a restrictive state to a permissive state, b) temporary operation in isolated mode, wherein: - if a state divergence persists beyond a first predetermined duration (k), operation of the computer changes to an isolated mode (208) in which the master computer does not take into account the output states of the slave computer and where the slave computer does not provide more trips abroad, - for the slave computer, the isolated mode is a mode setting consistent with the master computer - in order to be able to run again in redundant mode, the slave computer asks the computer master switch to redundant mode in this mode change is possible only if the slave computer made the request after finding that converges with the output stages of the master computer.