Some embodiments include a lock cylinder comprising: a plug assembly having a front portion and a back portion; a housing shell within which the plug assembly is rotatably disposed, wherein the housing shell includes a notch; wherein the back portion of the plug assembly comprises: a locking pin that is movably disposed, and wherein the locking pin is configured to prevent a rotation of the plug assembly when the locking pin is engaged in the notch and prevented from retracting by a multi-stable mechanism; and the multi-stable mechanism having at least two stable configurations corresponding to respectively to a locked state and an unlocked state, wherein the multi-stable mechanism can maintain the stable configurations without consuming energy; wherein, at a first stable configuration, the multi-stable mechanism prevents the locking pin from retracting, and, at a second stable configuration, the multi-stable mechanism enables the locking pin to retract.

A lock cylinder comprises a cylinder housing, a disk housing rotatably supported about a cylinder axis in the cylinder housing and a plurality of rotatably supported disk tumblers arranged along the cylinder axis in the disk housing, wherein each disk tumbler has a reception opening for a key, a blocking cut-out at the outer periphery for an at least partial reception of a blocking pin aligned in parallel with the cylinder axis and a fixing cut-out provided offset from the blocking cut-out at the outer periphery for an at least partial reception of a core pin aligned in parallel with the cylinder axis. The disk tumblers are rotatable from a starting position with a removed key into an end sorting position by a rotation of the introduced key in the latching direction, in which end sorting position the blocking cut-outs of all the disk tumblers are oriented in alignment with one another, viewed in the direction of the cylinder axis. The fixing cut-outs of all the disk tumblers are oriented in alignment with one another in the end sorting position, viewed in the direction of the cylinder axis. The lock cylinder is adapted such that, on a further rotation of the disk tumblers out of the end sorting position in the unlatching direction, the core pin first engages into the fixing cut-outs and the blocking pin only then engages into the blocking cut-outs.

Some embodiments include a lock cylinder comprising: a plug assembly having a front portion and a back portion; a housing shell within which the plug assembly is rotatably disposed, wherein the housing shell includes a notch; wherein the back portion of the plug assembly comprises: a locking pin that is movably disposed, and wherein the locking pin is configured to prevent a rotation of the plug assembly when the locking pin is engaged in the notch and prevented from retracting by a multi-stable mechanism; and the multi-stable mechanism having at least two stable configurations corresponding to respectively to a locked state and an unlocked state, wherein the multi-stable mechanism can maintain the stable configurations without consuming energy; wherein, at a first stable configuration, the multi-stable mechanism prevents the locking pin from retracting, and, at a second stable configuration, the multi-stable mechanism enables the locking pin to retract.

A key or a key blank for a disk cylinder having a plurality of rotatably supported disk tumblers has a key shaft having a shaft cross-section that comprises a first end section, a second end section and a connection section along a longitudinal axis, said connection section connecting the first end section and the second end section to one another. The connection section is narrower than the two end sections and has two longitudinal edges that are aligned in parallel with one another and that extend obliquely to the longitudinal axis of the shaft cross-section between the two end sections.