Method and system for testing subscriber loops using touchtone telephone signals

Abstract

A subscriber loop test apparatus relates to the testing of a subscriber loop by the use of a touchtone telephone. The touchstone buttons on a telephone provide Dual-Tone, Multiple Frequencies for each key pressed. For example, referring to FIG. 1, pressing the ‘3’ key causes tones at 697 and 1477 Hz to be sent across the telephone line. Pressing a sequence of keys provides discrete coverage of the frequency band from 697 to 1477 Hz, through the use of the touchtone telephone. The frequency band from 697 to 1477 Hz can be characterized in this fashion. Information about the line: loop loss (loop length), presence of bridge taps (i.e., excessively long bridge taps in particular) or loading coils, and the presence of Digital Loop Carriers (DLCs), et cetera. The use of the switch-hook flash provides the ability to determine the channel (impulse) response of the loop, including any noise and hum that may be on the loop due to imbalance or coupled interference.

Dependencies are inferred from the claim text.