The ZVEI Automation Association has adopted a new ZVEI recommendation for the classification of binary 24 V interfaces with testing in the area of functional safety. The recommendation presents - based on the current state of the art - a concept for the classification of safe electronic 24 V interfaces. The proposed classification and labeling makes it possible for the first time to see at a glance which actuators and sensors from different manufacturers are compatible with each other for the respective application. In the future, the user will thus have the advantage of functional safety on the one hand and significant time savings in the engineering process on the other. In addition to the members of the Technical Committee Safety Systems in Automation (TA Si), representatives of the Automation Initiative of German Automobile Manufacturers (AIDA) were also involved in the work. ZVEI recommendations have a quasi-normative character and represent the industry opinion of the companies represented in the automation trade association. The ZVEI recommendation with the keyword CB 24I is directly applicable and is also to be introduced as a standard proposal in international standardization.