Patent ID: 7235979

Claim:
A system for determining insertion loss of a telephone line under test (LUT) comprising: low frequency test hardware comprising: means for electrically stimulating the LUT at a first plurality of frequencies; means for determining for each frequency of the first plurality of frequencies an input impedance Z 2tr of the LUT at said frequency in response to the electrical stimulation at said frequency; means for determining values for at least two of Rs, Cs, Rp and Cp from Z 2tr at each frequency of the first plurality of frequencies, wherein Rs and Cs are the corresponding series RC equivalent components of Z 2tr and Rp and Cp are corresponding parallel RC equivalent components of Z 2tr ; and means for determining a first value insertion loss of the LUT as a function of a value of one of Rs, Cs, Rp and Cp determined at one frequency of the first plurality of frequencies and a value of another one of Rs, Cs, Rp and Cp at another frequency of the first plurality of frequencies; high frequency test hardware comprising: means for electrically stimulating the LUT at a second plurality of frequencies; means for determining for each frequency of the second plurality of frequencies an input impedance Zin of the LUT at said frequency in response to the electrical stimulation at said frequency and a length (d) of the LUT as a function of Zin at said frequency; means for determining for each frequency of a subset of the second plurality of frequencies a running standard deviation of the length d of the LUT, wherein the running standard deviation for each frequency is determined as a function of the lengths d determined at and below said frequency; means for determining which pair of adjacent frequencies of the subset of the second plurality of frequencies where the largest difference between running standard deviations occurs; means for determining a mean length (dm) of the LUT as a function of the lengths d of the LUT determined for each frequency at and below one of said pair of adjacent frequencies; means for determining a gauge of the LUT as a function of the running standard deviation of the one of said pair of adjacent frequencies; and means for determining a second value insertion loss of the LUT as a function of the gauge and the mean length dm; and means for comparing the values of the first and second insertion losses to an expected insertion loss value for the LUT and for designating one of said first, second and expected insertion loss values as the actual insertion loss value for the LUT.