A communication system for current-modulated transmission of data via a current loop—into which a master device and at least one slave device are looped. The at least one slave device has a switching means that is actuable by an evaluation and control unit and that is configured to short a current loop in the closed state, wherein the evaluation and control unit is configured to temporarily close and then reopen the switching means during a system configuration detection phase. An evaluation and control unit of the master device—is configured to detect when the at least one slave device is looped into the current loop.