Importance

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Abstract

A service-observing arrangement is disclosed for automatically detecting and classifying interrupted tone signals (such as audible ringing, busy, reorder, etc.) which appear on telephone lines. These signals have a certain 'pitch rate' discernible by the listener and caused by the combining of a plurality of separate tone signals. The line is scanned and the signals on the line are first passed through a filter to filter out all frequencies within the 'pitch rate' spectrum and are not fundamental components of the interrupted signal. The remaining signal is then modulated to produce a significant energy component at the 'pitch rate' only if legitimate signals are present. The ratio of pitch rate energy to total energy is then compared to threshold values and its cadence and power consistency are checked to identify the signal.

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First Claim