An electrical power and control unit was designed to power paralyzed or prosthetic upper limb joints in the mode of an artificial muscle. The system permits placing the components in any desirable location on the patient, interchanging terminal devices, actuating more than one joint by a single motor, and easy interfacing with a wide variety of orthotic and prosthetic components, including those of modular endoskeletal design. Sensor options for control-signal acquisition include a new skin motion sensor for shoulder disarticulation amputees and an improved myoelectric sensor.