Abstract: The method serves for calling a substation (USm) by a central station (Z) in a transmission system for the purposes of information transmission by way of a communication channel (m) called from a plurality of communication channels. The plurality of communication channels is subdivided into communication groups (GRI, GRII, GRIII) of the same property or the same parameter values. Within a selected communication group (GRII) a communication channel (m) is called, which is still communication-free. If all (n) communication channels of the communication group (GRII) are already busy, the central station (Z) goes into a waiting condition until at least one of the communication channels of the communication group (GRII) becomes communication-free.