An improved combination of a hardware and digital signal processing filter for detecting pick-up of a telephone call, solely through audio information on the telephone line, is disclosed. The apparatus employs a high gain band pass filter (28) with no automatic gain control, the output of which goes to a window comparator (30). The output from the window comparator (31) goes to a digital high pass filter (32) and from there to an integrator 37 for providing a digital output signal (40) indicative of the presence or absence on the telephone line of a signal exceeding a predetermined magnitude within the filter pass band. The digital signal is then processed by an intelligent digital filter having a set of predetermined threshold values of durations for states of the digital output signal, by which determinations of pick-up are made. The digital filter is adaptive and learns the durations high and low states of the digital output signal as they occur, subsequently checking for deviations from previously learned valid values. The digital filter includes a digital phase lock loop which will lock onto a periodic but asymmetric pattern in the digital output signal and declare pick-up when lock is lost.
Please note there is up to 60 days of latency in this Status indicator for certain status conditions. You can obtain up-to-date Status indicator readings by ordering PAIR for the file.
An application with the status "Published" (which means it is pending) may be recently abandoned, but not yet updated to reflect its abandoned status. However, an application filed less than one year ago is unlikely to be abandoned.
A patent with the status "Granted" may be recently expired, but not yet updated to reflect its expired status. However, it is highly unlikely a patent less than 3.5 years old would be expired.
An application with the status "Abandoned" is almost always current, but there is a small chance it was recently revived and the status not yet updated.
This priority date is an estimated earliest
priority date and is purely an estimation. This date should not be
taken as legal conclusion. No representations are made as to the
accuracy of the date listed. Please consult a legal professional
before relying on this date.