Input: yellow handle.
Output: blue shaft.
Two orange pins are fixed to the handle.
Two green studs are fixed to a hub fixed to the shaft.
The studs are inserted into holes on the handle. The hole diameters are a bit larger than the ones of the studs.
Violet pins are placed in the wedge-shaped space between the blue hub and the outer stationary disk (in glass). Red spring maintains permanent contact of the violet pins with them.
When the handle turns clockwise (yellow arrow), the left orange pin pushes the left violet pin, prevents its wedge action and the handle makes the blue shaft turn clockwise thanks to the green studs.
When the handle turns counter-clockwise (green arrow), the right orange pin pushes the right violet pin, prevents its wedge action and the handle makes the blue shaft turn counter-clockwise thanks to the green studs.
When an unintended clockwise torque (red arrow) is applied to the blue shaft, the shaft can not rotate because of the wedge action of the left violet pin.
When an unintended counter-clockwise torque (pink arrow) is applied to the blue shaft, the shaft can not rotate because of the wedge action of the right violet pin.
In brief, the rotation can be transmitted from the yellow handle to the blue shaft.
The transmission in reverse direction (from the blue shaft to the handle) is impossible.
In other words, it is possible to adjust angular position of the blue shaft by turning the yellow handle. The adjusted position is kept unchanged regardless of any torque applied to the blue shaft.
The video shows case of manually operated valve in pipe.have the similar working principles.