An example method involves electrically coupling first and second nodes of a device to a port of a digital subscriber line access multiplexer (DSLAM) and to a first end of a communication circuit. The communication circuit facilitates electrical coupling of the port of the DSLAM to a central office switch at a second end of the communication circuit. A signature circuit is electrically coupled between the first and second nodes to generate a signature signal in response to a test signal injected onto the communication circuit at a second end of the communication circuit. The signature signal has a magnitude substantially proportional to the test signal. First and second conductors of the communication circuit are electrically coupled to respective ones of the first and second nodes. Third and fourth conductors of the port of the DSLAM are electrically coupled to respective ones of the first and second nodes.