Ultra Dual Channel TENS TENS is an abbreviation of Transcutaneous Electrical Nerve Stimulation. Transcutaneous means "across the skin". The rest are reasonably obvious: electricity that stimulates the nerves. In simple terms, a TENS unit stimulates your nerves via an electrical current through your skin. Modified electrical pulses are then passed from the TENS unit, via the lead wires and electrodes, to the nerves which lie underneath the skin surface. The TENS unit is usually a small battery operated box which produces pain relieving electrical pulses. The Ultra Dual Channel TENS allows the user to use either 2 (single channel) or 4 (dual channel) self-adhesive electrodes applied to the skin and attached to the TENS unit with lead wires for full control.