This device measures 60x25x100mm and with diodes protection to allow current flow in one direction. Two built-in switches permit easy polarity reversal to treat 4 points (i.e., 2 separate cords) without disturbing the patient. The standard 3.5mm jack, alligator clip wires are required to use this unit. Insert normal alligator clip electrodes with 3.5 mm jack into CH1 and /or CH2. Setting A results in- black and + red clip. Setting B results in + black and - red clip. The - clip is generally connected to the area of excess or negative polarity. No battery required.