An electrode assembly comprising: an electrode configured to provide electrical contact with a subject's skin through a subject contact surface, the electrode comprising an electrode base pad having a first contact surface; and a connector assembly configured to electrically connect the electrode to an external electrical apparatus to transfer electrical signals between the subject's skin and the external electrical apparatus, the connector assembly comprising: a housing having a second contact surface, the second contact surface being configured to be magnetically and electrically coupled to the first contact surface of the electrode base pad; and an electrical connector configured to connect the second contact surface to the external electrical apparatus; wherein the electrode base pad forms a generally flat back surface on the side of the electrode opposite the subject contact surface and a detent in the flat back surface, the first contact surface being located in the detent; and the first contact surface is inset of the flat back surface of the electrode base pad thus forming an edge around the periphery of the first contact surface, enabling the second contact surface to be received in the detent; the electrode assembly further comprising a current spreader disposed between the first contact surface and the subject contact surface, and a gel layer disposed between the current spreader and the subject contact surface; characterized in that, measured in a plane parallel to the first contact surface, the gel layer has a larger area than the current spreader. an electrode configured to provide electrical contact with a subject's skin through a subject contact surface, the electrode comprising an electrode base pad having a first contact surface; and a connector assembly configured to electrically connect the electrode to an external electrical apparatus to transfer electrical signals between the subject's skin and the external electrical apparatus, the connector assembly comprising: a housing having a second contact surface, the second contact surface being configured to be magnetically and electrically coupled to the first contact surface of the electrode base pad; and an electrical connector configured to connect the second contact surface to the external electrical apparatus; a housing having a second contact surface, the second contact surface being configured to be magnetically and electrically coupled to the first contact surface of the electrode base pad; and an electrical connector configured to connect the second contact surface to the external electrical apparatus; wherein the electrode base pad forms a generally flat back surface on the side of the electrode opposite the subject contact surface and a detent in the flat back surface, the first contact surface being located in the detent; and the first contact surface is inset of the flat back surface of the electrode base pad thus forming an edge around the periphery of the first contact surface, enabling the second contact surface to be received in the detent; the electrode assembly further comprising a current spreader disposed between the first contact surface and the subject contact surface, and a gel layer disposed between the current spreader and the subject contact surface; characterized in that, measured in a plane parallel to the first contact surface, the gel layer has a larger area than the current spreader.