Lock having an external bolt unlocking device

A lock comprising a day bolt (1) and a night bolt (2), each slidable between an extended locking position and a retracted releasing position, said day bolt (1) being urged by a spring (8) to the extended locking position and being retractable by a handle-operated tumbler to the releasing position, said night bolt (2) being urged by a spring to the retracted releasing position and being lockable in both the locking position and the releasing position by a locking mechamisn (14) pivotable by a key bit or by the nose (10) of a lock cylinder (11) against a spring biasing force (18) to a position wherein the night bolt (2) is slidable and further including an actuating member (20) for the locking mechanism (14) operable from outside the lock, characterized in that in a lock wherein the locking mechanism is designed as a packet of tumblers (14) through which extends a locking pin (9) projecting laterally from the night bolt (2), the actuating member for the locking mechanism is a swivelling lever (20) having an arm (21) projecting from the lock housing (4), and arranged to be retained by an energized electric magnet (25) in a position in which the lever (20) does not influence the tumblers (14), said lever (20) being loaded by a spring which tends to move it in a direction wherein the lever (20) loads the tumblers to the position releasing the night bolt (2), all this without influencing the day bolt (1).