| 摘要 |
An apparatus and method are provided for a data communications device, such as a modem (100, 101) or facsimile machine, to detect and discriminate various amplitude modulated signals, such as an ANS signal of the ITU V.25 protocol and an ANSam signal of the ITU V.8 protocol, which may be subject to impulse distortions (FIG. 5B). The apparatus and method embodiments band pass filter (204) an incoming signal at a first frequency, and dynamically limit (208) any impulse distortions of the incoming signal to a limit threshold (211). The limit thresholds may be dynamically determined by rectifying (209) and low pass filtering (210) the band pass filtered signal to determine a low frequency average magnitude level of the incoming signal, with the limit thresholds set as a predetermined variance from this low frequency average magnitude level. The various frequency components of the amplitude modulated signal may then be discriminated by rectifying (215) and band pass filtering (217) at a second frequency, such as the frequency of the amplitude modulating component. Various detectors (205, 206) then determine the type of information present in the incoming signal, such as whether the signal is an ANS signal or an ANSam signal.
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