Adaptive pulse width time domain reflectometer

A method for using a time domain reflectometer (TDR) to locate a fault in a digital subscriber line (xDSL) having a characteristic impedance, the method comprising:

• a) providing a TDR transmitter and receiver;
• b) transmitting at least one launch pulse into the xDSL with the TDR transmitter and initiating a start time in a timebase;
• c) receiving a return signal trace from the xDSL with the TDR receiver;
• d) amplifying the return signal trace from the xDSL with an adjustable gain amplifier;
• e) digitizing the amplified return signal trace to generate an array of digital samples and sampling time information from the timebase;
• f) recording the array of digital samples and sampling time information;
• and
• g) differentiating the array of digital samples numerically by selecting pairs of digital samples separated by a time offset that increases, for subsequent pairs from the same launch pulse, as a function of elapsed time from the start time, and generating an arithmetic difference between each selected pair.