Methods of and apparatus for testing telephone subscriber loop to locate a fault relative to a reference point

摘要

Methods and a system of this invention are used to determine whether a fault in a subscriber loop is located between a telephone central office and a reference point or between the reference point and subscriber terminal equipment without opening the loop. Included in the system are two current interrupter networks one of which is connected in series with the tip conductor and one in series with the ring conductor. If a fault exists between the central office and the reference point, the application of a test signal causes a constant current reading on a meter at a test center. On the other hand, if a fault is present in the loop beyond the reference point, an oscillatory current reading appears on the meter. The system also includes a recognizable impedance termination network which is connected between the tip and ring conductors of the subscriber loop to facilitate testing for opens in the tip and ring conductors.