The EtherCAT ® Fieldbus Coupler connects EtherCAT ® to the modular WAGO I/O System. The fieldbus coupler detects all connected I/O modules and creates a local process image. This process image may include a mixed arrangement of analog (word-by-word data transfer) and digital (bit-by-bit data transfer) modules. The upper EtherCAT ® interface connects the coupler to the network. The lower RJ-45 socket may connect additional EtherCAT ® devices to the same line. EtherCAT ® (Ethernet Control Automation Technology) is a real-time ETHERNET solution designed for industrial automation applications and characterized by high performance, flexible topology and simple configuration. With EtherCAT ® , the costly ETHERNET star topology can be replaced with a simple line or tree structure. The address selection switch is used to set an Explicit Device ID (EDI), which allows a fixed address to be assigned to an EtherCAT ® slave.