Omron electroTHERAPY Pain Relief System, this TENS’s unit sends electro pulses across the surface of the skin and along the nerve strands. The pulses help prevent pain signals from reaching the brain. Tens devices also help stimulate your body to produce higher levels of its own natural painkillers, called "Endorphins". The Omron electroTHERAPY unit, is best used as soon as pain begins to help prevent the pain from becoming worse, or even chronic.