System for pre-qualifying telephone transmissions line for XDS communication services. The system includes a modem (10), located at the customer premises to be connected . The modem (10) analyzes actual signals to determine the electrical characteristics of the communication channel associated with the customer premises. The modem (10) includes a transmitter (26), receiver (26) and controller (30) to generate test signals and receive responses. The modem (10) then analyzes the data to generate an output value indicative of the electrical characteristics of the communication channel being tested. This output value is then displayed (48) to a user or transmitted over the communication channel to a network. The system thereby eliminates the necessity of dispatching a technician to test the telephone line, and provides more accurate test results than those achievable at the network side of the connection alone.