Interferential Analog Unit works by crossing two independent frequencies which work together to intercept the transmission of pain messages, This unit differs from TENS units as it provides for deeper skin penetration, Since the interferential stimulation is concentrated at the point of intersection between the electrodes, it is mainly used for localized areas where deep penetration is desired, IF 4000 units are easy to operate and the kit also includes AC Adapter, Dual Channel, Multi mode Selector Switch, Electrode Switch, Power on Indicator Light, Low Battery Light, Frequency Control, Amplitude Control, Specifications:, Carrier Frequency: (4000 +/- 10%) Hz, fixed, Difference Frequency: (1+/- 0, 5)~(150 +/- 10%)Hz, adjustable, Output Voltage: (16 +/- 2, 5)Volts, (500 ohm Loading), Waveform: Symmetric biphasic square, Pulse Width: (125 +/- 10%) microseconds for each phase, Power Source: 9V alkaline battery or AC adapter, Four Frequency Shift: Continuous, 1/1 abrupt, 8/8 abrupt, 10/10 ramped Options, Includes:, Stimulator, Lead Wires (New FDA compliant), 4 Self-stick Hypoallergenic, Reuseable Electrodes, 9 Volt Battery, 110V Adaptor, Hard Plastic Carrying case, Instruction Booklet, SKU: PMDS002