A mechanism of low cost and easy mounting, provides resistance to rotation of a coupling nut (14) of an electrical connector about the barrel (12) of the connector, and provides a higher resistance to rotation in one direction (U) than the opposite direction (M). A toothed ring (44) with a circle of teeth, is fixed to the barrel. The mechanism includes a washer (42) with projections (70, 72) that engage the teeth of the ring to ride over them during nut rotation, and thereby provide resistance to nut rotation. The washer is bent to form a spring to bias its projections against the teeth of the toothed ring. The washer also has ears (75, 76) that fit into slots in the nut to prevent washer rotation relative to the nut. The teeth of the toothed ring have first sides that are steeper than its second sides to provide higher resistance to rotation in one direction.