An electrode for use in cooperation with a signal-receiving apparatus is the subject matter of this invention. The electrode receives an electrical signal from a subject, which signal is then observed. The electrode includes an electrical half cell. The half cell includes a metal and an electrolyte solution. A diaphragm holds the electrolyte in contact with the metal. The diaphragm is sufficiently permeable to allow ionic conduction between the surface of a subject and the electrolyte.