T.E.N.S. stands for 'Transcutaneous Electrical Nerve Stimulation'. It uses a very small electrical current, which passes across the nerve carrying the pain signal to the brain. This affects the ability of the nerve to transmit the pain signal. If the brain receives no signal, you feel no pain. The unit has 6 different treatment regimes which are automatically controlled to give a measured treatment of 40 minutes. The controls are simple and easy to use. It is very small and discreet, and has a clip to attach to a belt or clothing to aid portability. It is supplied with a case, 2 contact pads, 2 cell batteries and operating instructions.