现场总线是许多任务业用通信协定的总称，一般用在即时分布式控制系统，IEC 61158是有关现场总线的标准，不过也有一些现场总线未列在IEC 61158中，如Modbus、LonWorks、CANopen等。

一个复杂的自动化系统（例如组装生产线）会需要一个有组织的控制系统阶层才能运作。在此阶层的顶端一般是人机界面（Human Machine Interface, HMI），可以让操作员监控及使用此系统。中间层则由许多可程序逻辑控制器（PLC）组成，PLC之间借由网络系统（如Ethernet）传递数据。低层则是由现埸总线连接PLC及传感器、致动器、马达、开关、阀门、接触器等实际动作或侦测的组件。

Fieldbus is the name of a family of industrial computer network protocols used for real-time distributed control, standardized as IEC 61158.

A complex automated industrial system — such as manufacturing assembly line — usually needs a distributed control system—an organized hierarchy of controller systems—to function. In this hierarchy, there is usually a Human Machine Interface (HMI) at the top, where an operator can monitor or operate the system. This is typically linked to a middle layer of programmable logic controllers (PLC) via a non-time-critical communications system (e.g. Ethernet). At the bottom of the control chain is the fieldbus that links the PLCs to the components that actually do the work, such as sensors, actuators, electric motors, console lights, switches, valves and contactors.