a paying out / winding in device eliminates torsion in a line in a rotary connection betweeen a fixed member and a mobile member to which respective ends of the line are fixed . this device comprises a fixed spool carrying a relatively small number of turns and fastened to the fixed member . a mobile spool near and coaxial with the fixed spool carries a relatively small number of turns and is fastened to the mobile member . an arm rotatable about the axis of the fixed and mobile spools carries a satellite pulley at its free end . it is rotatable about an axis inclined at a relatively small angle to the axis of the fixed and mobile pulleys . when rotating more slowly than the mobile spool , it transfers line from the mobile spool to the fixed spool or vice - versa . the arm is rotated by a system which comprises at least one sliding coupling having a primary member , a secondary member fastened to the arm and a first freewheel mechanism coupling the primary member to the mobile spool . a second freewheel mechanism couples the secondary member to the fixed spool .