In one embodiment, the method includes determining at least one value that depends on an attenuation of a signal transmitted over a telecommunication line to a DSL modem or received over the telecommunication line from the DSL modem; detecting depending on the value that the DSL modem is coupled with the telecommunication line via a DSL splitter in such a way that the DSL modem is connected to a different connector of the DSL splitter than a modem connector of the DSL splitter, which modem connector is intended for being connected with the DSL modem; determining a loop length value of the telecommunication line; and determining a threshold depending on the loop length value, wherein the detecting is based on comparing the threshold with the value.