A method for connecting an expansion module to a programmable electric switching device includes initiating a recognition mode within the switching device during which an interrogation is carried out as to whether or not the connected expansion module is initializable. If the expansion module is not initializable, no data is exchanged between the switching device and the expansion module. If the expansion module is initializable, the switching device switches into an expansion communication mode in which data exchange takes place under the control of the operating system of the expansion module.