This TENS unit is used mainly among Physiotherapists and Electro-acupuncturists. Its bi-phasic dual channel professional qualities include Pulse Rate, Pulse Width and Intensity adjustment as well as Burst, Continuous and two Modulation modes. Its two frequency ranges are adaptable from 1.3-200Hz + 8,000-12,000 Hz. With a timer, low battery indicator and mains option, this portable TENS machine is a 'must' for the professional on-the-move or for those of you who simply want the best.