| 摘要 |
PURPOSE: A method for detecting a telephone call terminating signal is provided to detect whether or not a telephone call is ended by carrying out correlation analysis for a signal transmitted from a PSTN (Public Switched Telephone Network) instead of frequency analysis of a tone signal. Therefore, a tone signal region is accurately detected without an additional frequency analysis, and a terminating signal generated at a voice signal and a switchboard is also accurately detected. CONSTITUTION: A telephone call-ending signal detector comprises a signal input (10), an analog/digital converter (20), a cycle detector (30), a calculator (40) and a telephone call-ending signal detecting unit (50). A method for detecting a telephone call-ending signal is processed in following sequence. The signal input (10) receives a voice signal or a tone signal from a PSTN (Public Switched Telephone Network). And then, the analog/digital converter (20) converts a signal corresponding to the output of the signal input (10) into a digital signal. The cycle detector (30) detects a cycle of the output of the analog/digital converter (20), and the calculator (40) carries out correlation as to the analog/digital converter (20). The telephone call-ending signal detecting unit (50) detects the telephone call-ending signal based upon the detecting results from the cycle detector (30) and the calculator (40). If the converted digital signal has a regular cycle and the correlated value is above a certain level, the converted digital signal is regarded as the telephone call-ending signal. That is to say, the telephone call-ending signal has a correlated value larger than a certain level. In case a tone signal having a noise is correlated, regions consisting of only noises and signals respectively are distinguished because the correlated signal is a large signal above a certain level and a signal close to zero (0) is generated in a noisy section. Having an irregular cycle, a voice signal is distinguished from the telephone call-ending signal.
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