Blue and green shafts rotate around a fixed axis.

Red spring maintains contact between yellow sprag and V-shaped groove of the green shaft.

The arrows show which link is the driving at different times.

When the blue shaft is driving, its two way rotation can be transmitted to the green shaft only in clockwise direction.

When the green shaft is driving, its two way rotation can be transmitted to the blue shaft only in antclockwise direction.

If the green shaft is kept immobile, the blue shaft can rotate only anticlockwise. It is braked automatically when rotating clockwise (mechanism for preventing reverse rotation).