magnetic field an electrical field an electromagnetic field a signal based on an interruption of a light barrier or a force producing a pressure signal according to a third exemplary embodiment the first substep can comprise that the exchange signal as is transmitted from the exchange signal generator 14 to the field device 10 to be exchanged e g a communication link 36 which can be designed bidirectionally can be used for this purpose once the field device 10 to be exchanged is identified the identification record id is thereupon transmitted to the control unit 4 for identification of the field device 10 to be exchanged according to a first exemplary embodiment the second substep can comprise that following reception of the exchange signal as the field device 10 to be exchanged transmits the identification record id of the field device 10 to be exchanged to the control unit 4 for this purpose e g the data exchange link 6 can be used thus the field device 10 to be exchanged informs the control unit 4 that an exchange is impending this exemplary embodiment is particularly efficient when the first substep has been performed in accordance with the second or third exemplary embodiment according to a second exemplary embodiment the second substep can comprise that the control unit 4 checks at intervals whether an exchange signal as is present and following the presence of the exchange signal as the identification record id of the field.