The invention relates to a very general method for the random diversification of a nucleotide sequence S by PCR while preserving the identity of some domains of said sequence S; the invention also relates to a bank of nucleotide sequence thus diversified, and to diversified proteins obtained by the expressions of the nucleotide sequences in an appropriate host. In some examples, the method senses the location of an upper joint to determine when the lifting device should begin decelerating prior to stopping the ascent of a lower joint at a target elevation. A first receiver is oriented toward a first location within the predetermined area and receives reflected return signals of the transmitted signal.