A TENS and EMS cord, also called a lead wire, is a cable that connects the TENS or EMS device to the electrode pads placed on the skin. TENS (transcutaneous electrical nerve stimulation) uses these cords to deliver electrical currents to stimulate nerves for pain relief, while EMS (electrical muscle stimulation) uses them to generate impulses for muscle contraction and strengthening. The cord has a device-end plug (often a 2.5mm or 3.5mm mini-plug) and a pin-end that snaps onto the electrode pads.