Device and method for monitoring a maintenance mode of an elevator installation

The invention relates to a control unit (10) and to an elevator-monitoring apparatus (50) and to a method for monitoring a maintenance mode of an elevator installation (100). The control unit (10) has a controller (12) and a memory device (14), wherein the controller (12) is designed to receive a first signal when a locking device (18) of shaft door (16) is locked and to receive a second signal when the locking device (18) is unlocked. The controller (12) is also designed to compare a chronological signal sequence of first signals and second signals with a reference sequence stored in the memory device (14) for actuation of the locking device (18) and, if the signal sequence of the first signals and second signals matches the reference sequence, to end the maintenance mode and to release a car (52) of the elevator installation (100) for a traveling operation.