The inside flip top cover includes an instruction diagram to guide the user through five modes of operation; constant, width modulation, rate modulation and two different types of burst. A timer allows the patient to use the device for a specified period of time and a low battery indicator light illuminates when the AA batteries need to be changed. If the device is not correctly attached to the patient, the amplitude does not increase. The waveform is symmetrical, biphasic square wave with adjustable pulse rate and pulse width. Measures 4.2" x 2.9" x 1.4" (10.7cm x 7.4cm x 4cm) and weighs 3.35 oz (94.97 grams). Includes carrying case, 2 AA batteries and instructions. 3-year limited warranty.