A system and method is described for determining a condition of a communication line, such as the absence of a filter device on a digital subscriber line (DSL). A first signal characterized by a high upstream power is activated over the line, and a first set of parameters associated with the communication line is obtained. A second signal characterized by a low upstream power is activated, and a second set of parameters associated with the communication line is obtained. Comparison of first and second sets of parameters is indicative of a condition of the connection and presences or absence of a DSL filter on the communication line.