Proposed is a joining system (10) as well as a method of operating a joining system (10) for joining elements (20) onto components (22), in particular for the short-time arc welding of elements (20), such as metal studs (20), onto components (22), such as metal sheets (22), having a central unit (12), which comprises a control device (30) and connectable to which is at least one joining unit (14) from a selection of different joining units, each of which comprises at least two modules (16, 18). The control unit (30) is designed so as to recognise (S16, S28) the mutual compatibility of the at least two modules (16, 18) of a connected joining unit (14) as well as the compatibility of the connected joining unit (14) with the central unit (12).