The AllCare ProTens Machine is a dual channel TENS machine with adjustable pulse width, pulse rate, intensity, modes and an accurate timer of 15, 30 and 60 minutes, will stop output at pre-setting time. What are TENS and how do they work? Transcutaneous electrical nerve stimulation is a pain control treatment. It is often called TENS for short. A TENS unit is a portable, pocket-sized, battery-powered device. The TENS unit uses mild, safe electrical signals to help control pain and delivers the electrical signal to the body through a connection of a lead wire and self adhesive conductive electrode.