A swing analyzing device includes at least an angular velocity sensor, a data acquiring unit, and a motion detecting unit. The device includes an element forming the locking bolt formed of an elastically deformable rod protruding from the cover and terminating in a hook-shaped free end suitable for engaging under a rigid rib of the receiver of the frame and the key has a spur making it possible to elastically move the rod to disengage its hook-shaped end from the rigid rib. The frame of a mosaic video signal may comprise one or more small pictures and each of them may render a miniature version of a television program. Movement of the curtain relative to the sensor can be linear, pivotal, radial, or any other suitable movement.