Bus nodes are used in automation technology for communication between controller and field device, for example for exchanging data with a valve terminal. The universal concept is currently unique in fieldbus technology because the CTEU can be used as an autonomous unit for all valve terminals from Festo, whether standalone or integrated, and is therefore especially relevant for a wide range of applications in cost-oriented automation markets. The different interfaces are combined into just one connecting plug for greater ease of use. The design enables a clear-cut arrangement of all LEDs and switch elements.