Apparatus and method for measuring loop insertion loss single-endedly

1. A system for determining insertion loss of a telephone line under test (LUT) comprising:

means responsive to electrical stimulation of an input of the LUT at each frequency of a first plurality of discrete frequencies for determining values of at least two of Rs, Cs, Rp and Cp at each said frequency, wherein Rs and Cs represent an equivalent series RC input impedance of the LUT and Rp and Cp represent an equivalent parallel RC input impedance of the LUT; and

means for determining an insertion loss value 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.

2. The system of claim 1 , further comprising:

means responsive to electrical stimulation of an input of the LUT at each frequency of a second plurality of discrete frequencies for predicting a length d of the LUT at said frequency;

means for determining a running standard deviation of the length d of the LUT at each frequency of the second plurality of discrete frequencies, wherein the running standard deviation at each frequency is determined as a function of the predicted lengths d determined for the LUT at and below said frequency;

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 the pair of adjacent frequencies where the largest difference between running standard deviations occurs;

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 an insertion loss value of the LUT as a function of the gauge and the mean length dm.

3. The system of claim 2 , further comprising:

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.

4. A method of determining insertion loss of a telephone line under test (LUT) comprising:

(a) determining values of at least two of Rs, Cs, Rp and Cp at each frequency of a first plurality of discrete frequencies, wherein Rs and Cs represent an equivalent series RC input impedance of the LUT and Rp and Cp represent an equivalent parallel RC input impedance of the LUT; and

(b) determining an insertion loss value 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.

5. The method of claim 4 , further comprising:

(c) predicting a length d of the LUT from at least one measurement of the LUT at each frequency of a second plurality of discrete frequencies;

(d) determining a running standard deviation of the length d of the LUT at each frequency of the second plurality of discrete frequencies, wherein the running standard deviation at each frequency is determined as a function of the predicted lengths d determined for the LUT at and below said frequency;

(e) 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 frequency of a pair of adjacent discrete frequencies where the largest difference between running standard deviations occurs;

(f) determining a gauge of the LUT as a function of the running standard deviation of the one of said pair of adjacent frequencies; and

(g) determining an insertion loss value of the LUT as a function of the gauge and the mean length dm.

6. The method of claim 5 , further comprising:

(h) comparing the values of the first and second insertion losses to an expected insertion loss value for the LUT; and

(i) in response to said comparison, designating one of said first, second and expected insertion loss values as the actual insertion loss value for the LUT.

7. A system for determining insertion loss of a telephone line under test (LUT) comprising:

means responsive to electrical stimulation of an input of the LUT at each frequency of a first plurality of discrete frequencies for determining values of at least two of Rs, Cs, Ls, Gs, Rp, Cp, Lp and Gp, at each said frequency, wherein Rs, Cs, Ls and Gs represent equivalent series resistance, capacitance, inductance and conductance input values, respectively, of the LUT and Rp, Cp, Lp and Gp represent equivalent parallel resistance, capacitance, inductance and conductance input values, respectively, of the LUT; and

means for determining an insertion loss value of the LUT as a function of a value of one of Rs, Cs, Ls, Gs, Rp, Cp, Lp and Gp determined at one frequency of the first plurality of frequencies and a value of another one of Rs, Cs, Ls, Gs, Rp, Cp, Lp and Gp at another frequency of the first plurality of frequencies.

8. A method of determining insertion loss of a telephone line under test (LUT) comprising:

determining values of at least two of Rs, Cs, Ls, Gs, Rp, Cp, Lp and Gp, at each frequency of a first plurality of discrete frequencies, wherein Rs, Cs, Ls and Gs represent equivalent series resistance, capacitance, inductance and conductance input values, respectively, of the LUT and Rp, Cp, Lp and Gp represent equivalent parallel resistance, capacitance, inductance and conductance input values, respectively, of the LUT; and

determining an insertion loss value of the LUT as a function of a value of one of Rs, Cs, Ls, Gs, Rp, Cp, Lp and Gp determined at one frequency of the first plurality of frequencies and a value of another one of Rs, Cs, Ls, Gs, Rp, Cp, Lp and Gp at another frequency of the first plurality of frequencies.