... hours working, Software is easy operating, Win 7 System and USB transmission. Specification for Portable EMGEP System:Amplifier:Channels: 2/4 ... .c) Vision: full vision, half-field (left), 1 / 4 view (I, II, III, IV quadrant)d) Stimulation frequency: 1 ~ 20 times ... ) Free to edit, set the pattern or color pattern. (3) Flash (Configured with goggles)Stimulus frequency: 0.1 ~ 20Hz adjustable