Self-clamping descender comprising: - a first flange and a side wall extending perpendicularly from the first flange to form a clamping area, - a pulley arranged to come into contact with a rope and fitted in rotary manner around a first rotation shaft defining a first axis of rotation, the first rotation shaft being fixed to a support, - the support fitted movable in rotation around a second rotation shaft fixed to the first flange, the second rotation shaft defining a second axis of rotation, the support moving between a first position and a second position, the first rotation shaft, the second rotation shaft and the side wall extending in the same direction from the first flange, - a cam mounted on the support, the cam being movable in rotation with respect to the first flange around the second rotation shaft between a first position where the distance from the clamping area is minimal and a second position, the rope being designed to pass around the pulley and to pass between the cam and the side wall, the cam clamping the rope against the side wall when in the first position, the cam, the pulley and the side wall belonging to a same plane parallel to the first flange, - the first axis of rotation is offset from the second axis of rotation so that so that application of a force on the rope to make the pulley to rotate in the first direction of rotation (+) generates a force urging the cam away from the clamping area, and application of a force on the rope makes the pulley to rotate in the second direction of rotation (-) generates a force urging the cam towards the clamping area, the first rotation shaft being movable around the second axis of rotation and movable with respect to the rope clamping area, self-clamping descender characterized in that - the first axis of rotation is offset from the second axis of rotation by a smaller distance than a radius of the pulley, - the pulley is configured to only rotate in a first direction of rotation (+) around the first axis of rotation and to prevent rotation in the second direction of rotation (-) around said first axis of rotation, - the pulley is arranged to define a rope circulation path having a semicircle, the semicircle being formed by a groove in the pulley. - a first flange and a side wall extending perpendicularly from the first flange to form a clamping area, - a pulley arranged to come into contact with a rope and fitted in rotary manner around a first rotation shaft defining a first axis of rotation, the first rotation shaft being fixed to a support, - the support fitted movable in rotation around a second rotation shaft fixed to the first flange, the second rotation shaft defining a second axis of rotation, the support moving between a first position and a second position, the first rotation shaft, the second rotation shaft and the side wall extending in the same direction from the first flange, - a cam mounted on the support, the cam being movable in rotation with respect to the first flange around the second rotation shaft between a first position where the distance from the clamping area is minimal and a second position, the rope being designed to pass around the pulley and to pass between the cam and the side wall, the cam clamping the rope against the side wall when in the first position, the cam, the pulley and the side wall belonging to a same plane parallel to the first flange, - the first axis of rotation is offset from the second axis of rotation so that so that application of a force on the rope to make the pulley to rotate in the first direction of rotation (+) generates a force urging the cam away from the clamping area, and application of a force on the rope makes the pulley to rotate in the second direction of rotation (-) generates a force urging the cam towards the clamping area, the first rotation shaft being movable around the second axis of rotation and movable with respect to the rope clamping area, - the first axis of rotation is offset from the second axis of rotation by a smaller distance than a radius of the pulley, - the pulley is configured to only rotate in a first direction of rotation (+) around the first axis of rotation and to prevent rotation in the second direction of rotation (-) around said first axis of rotation, - the pulley is arranged to define a rope circulation path having a semicircle, the semicircle being formed by a groove in the pulley.