A method for operating a specific field device from a first group and a second group of field devices, wherein the first group exchanges data in an IP-based network, and the second group communicates at least via a non-IP-based connection, the method includes the following: transmitting multicast messages having an item of connection information via at least one portion of the field devices of the first group; integrating the operator device into the IP-based network; initiating a connection establishment with a field device of the second group; receiving the transmitted multicast messages by the operator unit so that the connection information is made available to the operator unit; generating a list of all field devices of the first group and the second group; selecting the specific field device using generated list; initiating a specific connection establishment with the specific selected field device; and operating of the specific selected field device with the mobile operator unit.
