T.E.N.S. (Transcutaneous Electrical Nerve Stimulation) is indicated under a physician's prescription for the symptomatic relief and management of chronic (long-term) pain and the treatment of post-operative or post-traumatic pain.
Standard Features:

Dual channels
LCD indicating operation modes and output
Three modes: Standard, Burst, Modulation
Includes: TENS unit, soft carrying case, instructions and accessories (four electrodes and lead wires)
Also required (not included): One 9-Volt alkaline battery

Federal Law (USA) restricts this device to sale by or on the order of a physician.