Abstract: A biometric device fitted to, or adapted for fitting to, an access control member including a fastening element which is movable, in use, between a position in which it prevents opening of a closure and a position in which it permits opening of the closure, and operating members operable to move the fastening element between the positions through the agency of drive-transmitting elements operatively connected between the operating member and the fastening element, the device including elements incorporated in, or adapted to be incorporated in, the drive-transmitting elements and operable under the control of a biometric sensor to interrupt and restore the drive between the operating members and the fastening element.