Methods of etching substrates with small critical dimensions and altering the critical dimensions are disclosed. The method comprises, at a first telecommunications platform, receiving a first request to set up a call to a subscriber station. A pivoting device with a pivot axis is each formed case between two adjacent link sections, so that two adjacent link sections are pivotable towards one other around a pivot axis substantially within a pivot plane which penetrates the pivot axis substantially perpendicular. The mechanism includes a rotation type regulation member which has a plurality of contact surface sites whose distances from a rotation center are different in a radial direction with respect to the rotation center.