A controller that also acts as a server that hosts the control software that communicates with lower-level control devices, such as Remote Terminal Units (RTUs) and Programmable Logic Controllers (PLCs), over an ICS network. In a SCADA system, this is often called a SCADA server, MTU, or supervisory controller.
NIST SP 800-82 Rev. 2
See Control Server.
NIST SP 800-82 Rev. 2 under Master Terminal Unit (MTU)