Method of predicting voltages in telephone line measurement
First Claim
1. A method of measuring characteristics of a two-wire telephone line a circuit model of which comprises resistive and capacitive elements connected between tip, ring, and ground terminals of the line, comprising the steps of:
- coupling source voltages via source resistances to the tip and ring terminals in a plurality of test conditions;
in each test condition, determining a steady state voltage of at least one of the tip and ring terminals; and
deriving characteristics of the resistive elements of the line from the source voltages, source resistances, and determined steady state voltages;
wherein the step of determining each steady state voltage of a terminal comprises the steps of;
sampling the voltage at the terminal with a predetermined sampling period to provide a predetermined set of sampled voltages; and
calculating a predicted voltage value, constituting the determined steady state voltage, from the predetermined set of sampled voltages using a closed form second order solution of the circuit model.
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Abstract
For measuring characteristics (resistance, capacitance, and foreign voltage) on a telephone line, source voltages are coupled via source resistances to the line in three test conditions and the parameters are calculated from steady state voltages at the terminals of the line. Each steady state voltage is predictively calculated from nine samples of the voltage at the terminal using a closed form second order solution of a circuit model of the telephone line derived from a transformation of the circuit model into the Z domain and using the matched pole-zero technique. The steady state voltages can thus be determined without waiting for transients, due to the time constants of the telephone line, to die out, resulting in much faster measurements for telephone lines with large time constants.
13 Citations
14 Claims
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1. A method of measuring characteristics of a two-wire telephone line a circuit model of which comprises resistive and capacitive elements connected between tip, ring, and ground terminals of the line, comprising the steps of:
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coupling source voltages via source resistances to the tip and ring terminals in a plurality of test conditions; in each test condition, determining a steady state voltage of at least one of the tip and ring terminals; and deriving characteristics of the resistive elements of the line from the source voltages, source resistances, and determined steady state voltages; wherein the step of determining each steady state voltage of a terminal comprises the steps of; sampling the voltage at the terminal with a predetermined sampling period to provide a predetermined set of sampled voltages; and calculating a predicted voltage value, constituting the determined steady state voltage, from the predetermined set of sampled voltages using a closed form second order solution of the circuit model. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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Specification