Which of the following is NOT a type of Profibus?

Profibus (Process Field Bus) is a standard for fieldbus communication in industrial automation systems. It encompasses several specific protocols including FMS (Fieldbus Message Specification), DP (Decentralized Periphery), and PA (Process Automation). Each of these protocols is designed for different applications within an industrial setting.

FMS is a communication protocol that facilitates advanced process control and complex data exchange. DP is primarily used for connecting sensors and actuators in automation systems, making it suitable for real-time applications. PA, on the other hand, is used in process automation environments, including hazardous areas where intrinsic safety is necessary.

RTU, or Remote Terminal Unit, is not a type of Profibus; instead, it is a general device used in telemetry and SCADA (Supervisory Control and Data Acquisition) systems for data collection, processing, and transmission. Thus, identifying RTU as the choice that does not belong to the category of Profibus types highlights an understanding of industrial communication standards and their appropriate contexts.