A control unit for an elevator installation comprises a cover and a base. The control unit further comprises a lock which can lock the cover to the base or release it from the base. The lock comprises a locking bar with a magnet, wherein this locking bar is movable back and forth between a closed position and an open position by movement of a magnetic lock on a surface of the cover. The locking bar with the magnet is stabilized in the closed position by a first magnetic element and the cover is locked. The locking bar with the magnet is stabilized in the open position by a second magnetic element and the cover is released.