Factory Link initiates a new fuzzy logic evaluation every 10 s. The DCS either uses the external set points generated by fuzzy logic or the internal set points entered by the operators. The operators can switch from the “manual mode” to the “fuzzy logic mode” and back. The “fuzzy logic mode” can only be activated when all the critical system variables are in a predefined safe range. The DCS automatically switches back into “manual mode” whenever a system variable exceeds the safe range. The fallback to “manual mode” also takes place if the communication between the DCS and Factory Link is interrupted.