| 摘要 |
A main computer which furnishes main engine control signals to initiate a predetermined operation of an internal combustion engine, outputs a monitoring signal whose state changes between a high and a low levels at predetermined intervals. The monitoring signal is watched by a main computer monitor, which maintains its output at a high level during repetition of the change of state in the monitoring signal and, in absence of the change of state in the monitoring signal, changes the state of its output between the high and a low levels at intervals longer than that of the monitoring signal. A backup computer which furnishes auxiliary engine control signals to initiate the minimum operational condition of the engine, monitors the output of the main computer monitor to detect a malfunction or abnormal operation of the main computer. When the number of the changes of state in the output of the main computer monitor exceeds a predetermined value, the malfunction of the main computer is judged to be serious so that the backup computer provides a switching request signal. Under the condition of existence of the switching request signal and that the backup computer is properly operating, switching from the main to the backup computer takes place.
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