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A remote terminal unit (RTU) is a multipurpose device used for remote monitoring and control of various devices and systems for automation. It is typically deployed in an industrial environment and serves a similar purpose to programmable logic circuits (PLCs) but to a higher degree. An RTU is considered a self-contained computer as it has all the basic parts that, together, define a computer: a processor, memory and storage. Because of this, it can be used as an intelligent controller or master controller for other devices that, together, automate a process such as a portion of an assembly line.
Remote terminal units are also known as remote telecontrol units.
Remote terminal units are more advanced versions of PLCs, which can only follow specific programming called ladder logic. An RTU is sophisticated and intelligent enough to control multiple processes without requiring user intervention or input from a more intelligent controller or master controller. Because of this capability, the purpose of the RTU is to interface with distributed control systems (DCS) and supervisory control and data acquisition (SCADA) systems by sending telemetry data to these systems. But in most cases, even intelligent RTUs are connected to a more sophisticated control system such as an actual computer, which makes their reprogramming, monitoring and control of the entire system easier for a user.
An RTU can also monitor a field's analog and digital parameters through sensors and data received from connected devices and systems; it then sends these data to the central monitoring station, as is the case in many industrial facilities like power, oil and water distribution facilities. An RTU includes a setup software that connects input and data output streams; the software can define protocols and even troubleshoot installation problems.
Depending on the manufacturer, purpose and model, an RTU may be expandable and custom fitted with different circuit cards including communication interfaces, additional storage, backup power and various analog and digital I/O interfaces for different systems. Because of their widely varying applications, RTUs come in vastly different hardware and software configurations and may not even be remotely compatible with each other. For example, RTUs used in telecommunication automation may not be usable at all for oil and gas applications as the processes and hardware systems used would be completely different.