Two side-by-side conductors that are separated by an insulator (as in a cable) have a characteristic impedance between them. If the distance between the conductors does not change, this impedance does not change. If the distance between them increases, the impedance goes up. If the distance between them decreases, the impedance goes down. Time Domain Reflectometers (TDRs) use simple transmission line theory and pulse reflection principles to detect these impedance changes along a cable. The TDR transmits high frequency electrical pulses that travel through the cable until a change in characteristic impedance is encountered. Depending on the nature of the impedance change either all or part of the transmitted pulse will reflect back to the TDR…..