The invention describes a welding device (1) or a current source (2), with a control system (4), preferably comprising a microprocessor controller with a memory unit, a power component (3), in particular a current-inverting source, and additional components such as a welding torch (10), a wire feed device (11), etc., which are connected to the welding device (1) or the current source (2) via appropriate interfaces. An add-on module (27) is connected to the control system (4) or to the current source (2) for identifying a person by means of biometric physical characteristics such as an electronic fingerprint, voice recognition, iris recognition, recognition of a facial shape, recognition of writing, etc. or alternatively a transponder code via a transponder system.