An apparatus (40) and method for switching a customer-premises telephone line (36) between a plurality of local telephone networks (35). The local telephone networks may have different electrical and operational characteristics. Using less than 100 micro-amperes of current from the telephone networks, the apparatus (40) requires no external power and performs its tasks without interfering with the normal operation of the telephone networks including test equipment, terminal equipment, data transmission on the telephone line and test equipment.The method involves monitoring electrical signals on both local telephone networks (35) and using this information to assign a weight to each network. The customer-premises telephone line (36) is switched to the telephone network having the highest weight. The advantages are the elimination of a service call by a technician to manually switch the customer premises telephone line (36), equal access by both service providers to the switch and a seamless interface to the telephone networks.