An electrode identification system (1) for defibrillators, comprising an electrode plug (2) adapted for connection to at least one electrode having a first pair of conducting contacts (6, 8), an identification element (10) connected between the first pair of conducting contacts, a second pair of conducting contacts (12, 14) for connection to the electrode, and a housing (16) providing a cavity (18, 20) which substantially encases the first and second pairs of conducting contacts and the identification element and an aperture through which ends of the first and second pairs of conducting contacts extend, a defibrillator socket (3) adapted for connection to a defibrillator and adapted for connection to an electrode plug having a first pair of conducting contacts (24, 26) for connection to the first pair of conducting contacts of the electrode plug, a second pair of conducting contacts (28, 30) for connection to the second pair of conducting contacts of the electrode plug and for connection to the defibrillator, and a housing (32) providing a cavity (34, 36) which substantially encases the first and second pairs of conducting contacts and an aperture through which ends of the first and second pairs of conducting contacts extend, and an electrode identification unit (4) adapted for connection to a defibrillator socket having a circuit comprising contacts for connection to the first pair of conducting contacts of the electrode plug via the first pair of conducting contacts of the defibrillator socket, a signal detector (42) connected to the circuit which detects a signal from the identification element of the electrode plug, and a processor (44) which uses a measure of the signal to determine an identification characteristic of the identification element of the electrode plug and from this identifies a category of the electrode connected to the electrode plug.
