A lamp comprises a light source (1), a battery (2) and a switch unit (3) which are electrically interconnected. The lamp's reliability, wear life and corrosion resistance are increased by the switch unit being a magnetic switch (3), which by an electrically insulating moulding material is moulded in the same unit as the light source (1) and the battery (2), and which is operated externally by a movable magnet (4).