Function

The feeler wheel runs along the rail. The claw that is connected to the wheel rests in the housing.

When the feeler wheel rolls over a catch, the claw is pushed into the rail. After the feeler wheel passes the catch the claw is pulled back into the housing by the spring.

If the downward speed is too high, the claw has no time to move back into the housing. The claw is driven against the catch and blocks movement. The claw is additionally pressed into the rail by the downward motion of the anchorage point. The anchorage point is not directly connected to the claw. Therefore, the claw can not be disengaged if the person climbs. The design of the blocking system guarantees that the block function is not impaired by spring breakage or contamination.