Method and apparatus for qualifying loops for data services

A method for analyzing a transmission line comprising:

• applying a common mode voltage having a frequency changing over a range of frequencies into the transmission line;
• determining phase of signals produced on each wire of the transmission line, in response to the applied voltage, relative to the applied voltage;
• detecting a peak in the determined phase;
• determining a frequency of the detected peak.

A method for qualifying a transmission line to propagate data signals, comprising:

• applying a common mode voltage having a frequency changing over a range of frequencies into the transmission line;
• determining phase imbalance in response to the applied common mode voltage;
• detecting a peak in the determined phase imbalance;
• determining a frequency of the detected peak.

A system for automatically qualifying a plurality of transmission lines, such system comprising:

• a switch coupled to terminating ends of the plurality of a transmission lines;
• a controller for feeding signals to the switch;
• a measurement unit coupled to the switch and the controller, such measurement unit being adapted to feed test signals from the measurement unit to a selected one of the transmission lines through the switch, such one of the transmission lines being selected in accordance with a control signal fed to the switch by the controller, such measurement unit isolating resistance imbalance between each of a pair of lines in the selected one of the transmission lines in response to the feed test signals fed to such selected one of the transmission lines;
• and wherein the controller, in response to the isolated resistance imbalance, is adapted to determine qualification of the selected one of the transmission lines for data signals.

A method of analyzing a telephone line having at least a first leg and a second leg, the method comprising the steps of:

• a) applying test signals to the first leg and the second leg to determine, at a first frequency and a second frequency:
• i) the capacitance between the first leg and ground;
• and
• ii) the capacitance between the second leg and ground;
• b) determining that no resistive imbalance exists when:
• i) the difference between the capacitance between the first leg and ground measured at the first frequency and the second frequency is below a threshold;
• and
• ii) the difference between the capacitance between the second leg and ground measured at the first frequency and the second frequency is below a threshold.