Telephonic communications – Supervisory or control line signaling – Signal receiver
Patent
1992-09-28
1995-10-17
Hofsass, Jeffery A.
Telephonic communications
Supervisory or control line signaling
Signal receiver
379283, 379351, H04M 322
Patent
active
054597846
ABSTRACT:
Multifrequency signals are detected in a received signal by extracting filter coefficients from the received signal, generating line spectrum frequency (LSF) parameters from the filter coefficients, and processing the LSF parameters to identify multifrequency signals. The LSF parameters are first examined to see if the lowest frequency represented by the LSF parameters is below a predetermined frequency, e.g., 600 Hz, and if so it is determined that the signal is not a multifrequency signal. The parameters are next examined to see if there are exactly two sharp frequency spectrum peaks, with a sharp peak being defined by two consecutive LSF frequencies separated by less than some predetermined frequency range, e.g., 60 Hz. Assuming there are two peaks, the locations of the peaks are examined to see if they correspond to the possible tone pairs, thereby identifying a particular multifrequency tone.
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Comsat Corporation
Hofsass Jeffery A.
Weaver Scott L.
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