Has the fail-safe system and its system the grade crossing control unit

摘要

PROBLEM TO BE SOLVED: To detect the failure of a key switch by issuing an alarm when there is a failure in the key switch and if a state of neither a first switching state nor a second switching state occurs for a first fixed time. ;SOLUTION: When a use stop key switch 1 is operated after an up use stop switch 2-1 or a down use stop switch 2-2 is operated, an interface does not recognize the operation thereof. Irrespective of the state of a system, if the contact of the use stop switch 1 indicates an error state for over a fixed time, the state of the system is changed to a safety shut-down state for causing the system to output a safe side output to fix its operation. Also, before the state of the system is changed to the safety shut-down state, an alarm is issued by a means such as buzzer sounding, alarm lamp lighting, alarm message displaying or the like.;COPYRIGHT: (C)1999,JPO