But the breaking force is depending on the line speed and the air gap between breaking plate and permanent magnets(small gap -> high break force; big gap -> low break force). So a perfect adjustment is only possible for one operating point. The air gap has to be adjusted to values that the driven and idler clips stay as long as possible in contact during the deceleration process for every possible line speed and deceleration rate. If the idler clip loses the contact to the driven clip, it is not allowed that the idler clip hit the previous driven clip. The time when the idler clip loses to contact to the driven clip should be as short as possible. Losing contact leads always to a more or less strong collision, which causes an oscillation in the system. The collision can be so strong that the driven falls out of the magnetic wave. But the air gap should also be not too small because this may lead to a breaking force which is higher than the force of the driven clip and the clip falls also out of the magnetic wave.