Abstract:
Unauthorized access to modules, especially modules in automation systems, is prevented by controlling access between modules and a central processing unit. At least one first device transmits an identifier to at least one of the central processing unit and a second device which evaluate(s) the identifier by comparison with at least one comparative identifier stored in the at least one of the central processing unit and the second device. Operation of the first device on the system is denied by the at least one of the central processing unit and the second device if the received identifier does not correspond to the comparative identifier.