A test system detects proper connection wiring in a connection frame between a customer's lines and a DSL Access Multiplexer (DSLAM). A multi-loop tester at a central office generates a test signal on low frequency lines to a customer's connection in a connection frame. A signature circuit is electrically connected between the customer's connection in the connection frame for the low frequency lines and the DSLAM. The signature circuit responds to the test signal and generates a signature signal. The multi-loop tester senses the signature signal to verify that the DSLAM is properly connected to the customer's lines.