BioStim SD Digital TENS. It is a compact, extremely durable and portable unit measuring 3.9" x 2.5" x 1.1" and weighs only 3.25 oz. The unit outputs an asymmetrical biphasic square waveform and includes adjustable pulse width (10-250US) and frequency settings (1-200Hz). The device can be turned up to 98mA to accommodate even the most high-demand patients. The device has large, easy to press buttons and no small dials, enabling ease of use by patients with dexterity issues. The lead wires are durable and easy to handle and install. The device closes, covering all of the controls to prevent any accidental changes during use for added safety. The large 1.5" x 1.75" display is easy to read. The belt clip is made of a durable polymer plastic and can be easily removed and replaced by the patient if necessary. The device automatically detects when the batteries are running low and a battery indicator light on the screen flashes, notifying the patient that the batteries should be changed or charged. The device has four programmable functions; Continuous, Cycled Burst, SD1, and SD2. When the device is turned off, it stores the last setting used by the patient, when the unit is turned back on, it displays the last settings for ease of use. The clinician can lock the device in place to ensure the settings are retained for the patient should the patient have trouble setting the device made possible by the "Patient Lock System" that, when activated prevents the patient from changing any of the set parameters. When the Patient Lock Systems is turned off, a "Patient Compliance Meter" is displayed showing how many hours the device was used. A timer allows the patient to use the device for a specified period of time. The device comes with lead wires; four 2" x 2" self-adhesive reusable electrodes; two AA Alkaline batteries and carrying case. 5 year warranty.