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That is, a on-site control unit also includes several digital input/output expansion units, which are connected to each other through a bus.

Essentially, the structural form and configuration requirements of the on-site control unit are consistent with the hardware configuration of the modular PLC. Operation station

The operation station is used to display and record process data from various control units, and is an operational interface for exchanging information between humans and production processes. Typical operation stations include host systems, display devices, keyboard input devices, information storage devices, and print output devices, mainly achieving powerful display functions (such as analog parameter display, system status display, multiple screen displays, etc.), alarm functions, operation functions, report printing functions, configuration and programming functions, etc.

In addition, the DCS operation station is also divided into an operator station and an engineer station. From a system functional perspective, the former mainly implements general production operations and monitoring tasks, with functions such as data collection and processing, monitoring screen display, fault diagnosis, and alarm.

The latter should not only have the general functions of an operator station, but also have functions such as system configuration and modification of control objectives. From a hardware device perspective, the engineer station and operator station of most systems are combined and distinguished by only one engineer keyboard.