US Patent 7097001 Elevator car door movement restrictor

An elevator door restrictor system for preventing an elevator door from being opened unless the elevator car is near a floor landing, utilizing battery backed electronics for sensing the presence of a building landing such that the system will continue to maintain the mechanism in the correct state, either locked or unlocked, even if the elevator car continues to move. Wherein even if the battery backup were to become completely discharged, the mechanism will remain in the last state, either locked or unlocked and prevent the elevator car door from being opened until an authorized person takes the appropriate step to move the car or open the car door.