As an auxiliary facility to assist a disabled patient to perform a normal walk, the crutch or the wheelchair is considered to provide an essential mobility as a mechanical facility. However, these facilities can not provide a basic function for these patients to sustain a standing position except a mechanical prosthesis. To control the activity of the prosthesis, a muscle membrane potential produced via an arm swing during the period of a walk is used as a control signal. In this paper, we adopt a dual ADC interface on a STM3210E-LK board to extract two kinds of muscle membrane potentials on a single arm. These two potential signals can be used to control the activities of the mechanical prosthesis. In the experiment we use these two potential signals to control the activities of a humanoid robot to simulate the activities of the mechanical prosthesis.