The electrodes used would vary based on the end application. If it's for personal use, we recommend dry electrodes. They do not use artificially applied electrolyte solutions or gels. They are made up of a graphite or metal-filled polymer such as silicone elastomer. However, if it's for public use then we recommend replaceable wet electrodes as they consist of a metallic conductor in contact with the skin with an artificially applied thin layer of an electrolyte gel between the metal and the skin to establish the contact. The electrodes are connected using high a impedance amplifier.