The Remote Link Unit---An Advanced Remote Terminal Concept

Remote terminal units are extensively used in digital automation systems to interface a central processing unit (CPU) to remotely located sensors and actuators. This paper presents a conceptual description of the remote link unit (RLU) which overcomes inherent limitations of remote terminal units. The RLU utilizes a single type of interface card to support most process I/O interfaces. The RLU identifies sensors, actuators, and subsystems through the use of electronic nameplates. Each nameplate provides information regarding device function, location, interface parameters, and calibration status. In addition it stores programs for device handling, engineering unit conversion, and device diagnosis. The RLU allows sensors and actuators to be relocated or substituted without requiring changes in the CPU software to correct device addresses or conversion constants. The electronic nameplate may also be used for inventory control, automatic calibration, and maintenance of devices.