System for acquiring and processing myoelectric signals in order to control a prosthetic arm, comprising a pair of positioned in a muscle in the residual limb of an arm that has been amputate in order to detect myoelectric signals an electrode positioned at a distance from said pair of electrodes, which acts as an earth system a myoelectric signal conditioning means and a prosthesis controlling and processing means which receives conditioned signals from the conditioning means. The prosthesis controlling and processing means includes a comparison means for comparing a muscle contraction time and a muscle contraction voltage with a threshold time and a threshold voltage, respectively and an activation means for activating at once motor which produces a pre-determined movement of the prosthesis in response to an activation signal transmitted from the aforementioned comparison means. The electrodes provide the myoelectric signal for activating different movements of the prosthesis, without the electrodes hazing to be changed to another muscle.
