• LAN Cable Testers perform this function using a Time Domain Reflectometer (TDR) that samples and analyzes the impedance of a link. Relative Impedance is measured as a function of length and each cable can be viewed in graphical format along its length to ascertain where the anomalies are located, whereas Characteristic Impedance is usually measured in a laboratory with complex test equipment such as an expensive network analyzer. The TDR measures relative impedance in the field to find crimps, kinks and/or stretched cable that would show up as a blips, peaks or valleys on the otherwise flat line graph of a good link. (also see FAULT FIND)