LSI System IV Interferential Muscle Stimulator distributed by LSI International offers both true interferential and premodulated interferential therapy. designed for relief of chronic, intractable pain and/or acute, post-traumatic pain, relaxation of muscle spasm, prevention or retardation of disuse atrophy, muscle re-education and maintaining or increasing range of motion. marketed as user friendly and features a microprocessor controlled for precise operation. intended to provide versatility of treatment from four channels (8 electrodes). It aims to allow treatment at two sites simultaneously. Side A and B provide separate timer and frequency control.