Zero-backlash coupling designs include safety-, metal bellows-, and servo insert-type couplings. The safety couplings use a pre-stressed Bellville spring to disengage servomotors within 2 to 4 msec, compared to a full second for conventional couplings. Metal bellows couplings are designed with high torsional stiffness and low inertia, avoiding the resonance problems of many high performance drives. And servo insert-type couplings increase dampening without deformation. Rimtec Corp., FAX (630) 325-1404.