Microcurrent electrical neuromuscular stimulator
A microcurrent electrical neuromuscular stimulator or MENS (also microamperage electrical neuromuscular stimulator) is a device used to send weak electrical signals into the body. Such devices apply extremely small microamp [μA] electrical currents (less than 1 milliampere [mA]) to the tissues using electrodes placed on the skin.
Source: Wikipedia — Microcurrent electrical neuromuscular stimulator (CC BY-SA 4.0)