Circuits and branches of single-degree-of-freedom planar linkages

Improved definitions for circuits and branches of mechanisms are proposed and discussed in application to planar linkages. The difficulty of circuit and branch identification for multi-loop planar linkages is introduced. The nomenclature used by various authors is correlated with the definitions proposed here. The danger of confusing circuits with branches is illustrated by demonstrating that mechanisms satisfying published 'branch defect' criteria may actually require disassembly to reach all desired positions, rendering them useless in practice. Furthermore, the published 'branch defect' criteria are shown to be irrelevant for some applications.