| 摘要 |
Method and apparatus for detecting far end speech in a telephone apparatus. A speaker (14) reproduces far end sound from a far end signal, when received by the telephone apparatus. A microphone (12) generates a near end signal from near end sound, for transmission from the telephone apparatus. A hybrid (24) which passes the near and far end signals from an external two wire link (30) to and from the speaker and microphone, on respective first and second paths (1, 2) of a four wire link (28). Muting of the near end signal is effected when signal derived from the first path (1) of the four wire link (28) is detected as being representative of a condition of existence of far end signal. Signal determined as representing sidetone signal deriving from the near end signal from the speaker (14), and appearing in the signal on the first path (1) of the four wire link (28), pursuant to traverse of part of near the end signal through the hybrid, is subtracted from the signal derived from the first path (1) of the four wire link (28). Existence of the condition of existence of far end signal is then determined on the basis of the result of the subtraction.
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