The Digital EV-804A Tens machine comes with multiple TENS therapy modes that will provide instant muscle pain relief. The Digital EV-804A TENS unit sends comfortable stim impulses through the skin that stimulates the nerve in the treatment area, acting as an electric massager, and calming the nerve. Treatment can be given on-demand or via timed therapy sessions up to 60 minutes. In many cases, this stimulation will deliver immediate pain relief. Pain relief varies by individual and by the type of pain you are in.