Neuromuscular Electrical Stimulation (NMES / EMS) otherwise know as a TENs stimulator or Electrical Muscle Stimulator.
I bought it years ago as part of my rehab for $180 after being hit by a car...I used it around ten times and now I don't use it because I am better. Perfect condition with all the part needed.
The EMS 2000 Muscle Stimulator is a dual channel analog muscle stimulation device that includes three operational modes: Constant, Reciprocal, and Cycled.