Control unit for controlling a fire damper or smoke evacuation shutter, said control unit comprising: an incoming axis; an outgoing axis designed to be coupled to the damper/shutter for opening and closing thereof; a gear box coupling the incoming and outgoing axes in rotation; a spring biasing said incoming axis, gear box or outgoing axis, the gear comprising a gear wheel towards a safety position of the damper; a locking means acting on the gear box, allowing to maintain the damper/shutter in an armed position against the force of said spring; said locking means comprising: an actuator body rotatably around an axis; a latch provided on the actuator body and said actuator body being biased by a bi-stable spring configured to maintain the actuator body in one of two stable positions, namely, a lock position, wherein the latch acts on the gear box, and an unlock position, wherein the latch stands clear from the gear box; said bi-stable spring forcing the actuator body into one of its bi-stable positions upon movement of the latch over a course of length L1, said length L1 being smaller than the distance L2 between two adjacent tooth of a gear wheel with which the latch cooperates or said length L1 being smaller than the depth D2 of the tooth/teeth of the gear wheel with which the latch cooperates; said actuator body interacting with a solenoid maintaining the actuator body in the lock position when in an unpowered state and allowing rotation of the actuator body to the unlock position when powered; and said actuator body comprising a secondary arm; the locking means further comprising a mechanical unlocking mechanism comprising a spring biased notch moveable between a first position, wherein the notch interacts with the secondary arm, thereby forcing the actuator body in the unlock position and a second position, wherein the notch allows the secondary arm to move in a position corresponding to the lock position of the actuator body. an incoming axis; an outgoing axis designed to be coupled to the damper/shutter for opening and closing thereof; a gear box coupling the incoming and outgoing axes in rotation; a spring biasing said incoming axis, gear box or outgoing axis, the gear comprising a gear wheel towards a safety position of the damper; a locking means acting on the gear box, allowing to maintain the damper/shutter in an armed position against the force of said spring; said locking means comprising: an actuator body rotatably around an axis; a latch provided on the actuator body and said actuator body being biased by a bi-stable spring configured to maintain the actuator body in one of two stable positions, namely, a lock position, wherein the latch acts on the gear box, and an unlock position, wherein the latch stands clear from the gear box; said bi-stable spring forcing the actuator body into one of its bi-stable positions upon movement of the latch over a course of length L1, said length L1 being smaller than the distance L2 between two adjacent tooth of a gear wheel with which the latch cooperates or said length L1 being smaller than the depth D2 of the tooth/teeth of the gear wheel with which the latch cooperates; said actuator body interacting with a solenoid maintaining the actuator body in the lock position when in an unpowered state and allowing rotation of the actuator body to the unlock position when powered; and said actuator body comprising a secondary arm; the locking means further comprising a mechanical unlocking mechanism comprising a spring biased notch moveable between a first position, wherein the notch interacts with the secondary arm, thereby forcing the actuator body in the unlock position and a second position, wherein the notch allows the secondary arm to move in a position corresponding to the lock position of the actuator body. an actuator body rotatably around an axis; a latch provided on the actuator body and said actuator body being biased by a bi-stable spring configured to maintain the actuator body in one of two stable positions, namely, a lock position, wherein the latch acts on the gear box, and an unlock position, wherein the latch stands clear from the gear box; said bi-stable spring forcing the actuator body into one of its bi-stable positions upon movement of the latch over a course of length L1, said length L1 being smaller than the distance L2 between two adjacent tooth of a gear wheel with which the latch cooperates or said length L1 being smaller than the depth D2 of the tooth/teeth of the gear wheel with which the latch cooperates; said actuator body interacting with a solenoid maintaining the actuator body in the lock position when in an unpowered state and allowing rotation of the actuator body to the unlock position when powered; and said actuator body comprising a secondary arm; the locking means further comprising a mechanical unlocking mechanism comprising a spring biased notch moveable between a first position, wherein the notch interacts with the secondary arm, thereby forcing the actuator body in the unlock position and a second position, wherein the notch allows the secondary arm to move in a position corresponding to the lock position of the actuator body.