METHOD FOR RECOGNIZING TELEPHONE TONES, DEVICE IMPLEMENTING THE METHOD, TELEPHONE DEVICE AND ANSWERING MACHINE PROVIDED WITH SUCH A DEVICE

摘要

Method and device for recognizing at least one tone emitted on a telephone network, each tone period comprising a sound phase wherein a 440 Hz signal is emitted, and a silence phase. In general according to this method, the presence of a periodical signal having the appearance of a tone, the duration of the period of said periodical signal is measured, the total measured duration is compared with at least one stored reference duration. When the result of the comparison is positive, the periodical signal is recognized as being the tone whose period duration corresponds to said reference duration. Application to telephone deviator and responders.