Single-ended DSL line tester

Telephone lines can have discontinuities caused by line faults, coils and bridge taps that impede transmission. Telephone companies (telcos) must locate and repair these faults in order to enable high-speed data transmission. It is useful for a telco to ´prequalify´ lines for future DSL services, so a customer can be promptly informed if high-speed services can be supplied This paper proposes a new technique called frequency domain reflectometry (FDR) to accurately locate impairments in telephone lines and determine the reflection magnitude caused by faults. The measurement produces a result similar to the well-known time domain reflectometer (TDR); however, DSP techniques are now applied to provide enhanced resolution and range beyond 3 km. In addition to reflection magnitude, the new technique can measure reflection angle which helps determine the nature of the fault (open circuit, short circuit, broken wire, coil, etc.).