Method and apparatus to determine whether a subscriber line is loaded or non-loaded

摘要

The method and apparatus to determine if a telephone subscriber line is loaded or non-loaded including circuitry to provide a signal having at least one given frequency which is coupled to a telephone subscriber line under test having a subscriber subset on-hook either directly or through the switching system such that this signal can be received from the subscriber line under test and analyzed to determine the value of at least one parameter of the subscriber line under test to determine whether the subscriber line under test is loaded or non-loaded. When the signal applied to the line has one frequency, the parameter involved is the real part of the on-hook impedance of the subscriber line under test and where a plurality of frequencies are employed, the parameter involved is either the change in the real part of the on-hook impedance of the subscriber line or a change in the phase angle of the on hook impedance of the subscriber line.