The cyan input shaft rotates two directions but the transmission is possible only for one. The rotation direction that tends to wind the spring is transmitted to the yellow output shaft due to friction force between the spring and the shafts. For the inverse direction the yellow output shaft may rotate if there is no braking force or load applied to it.
The helix spring needs not be fastened at either end; a slight interference fit is acceptable.
The spring helix direction decides the transmission direction.