Abstract: Equipment and methods are disclosed for testing inductively loaded telephone lines for loading irregularities. In brief, immittance magnitude measurements are used to determine the approximate frequencies of the poles and zeros of such a line and then a lossless ladder network comprising series inductors and shunt capacitors is synthesized wherein the pole and zero frequencies of the network are substantially equal to those previously determined. The network inductor values relate to the line loading inductor values while the network capacitor values relate to the distances between the loading inductors.