| 摘要 |
PURPOSE:To attain hand-free talking by switching automaticlly a transmission/ reception changeover switch depending on the presence or absence of voice input. CONSTITUTION:A signal inputted from a voice input section 1 is converted into a digital signal by an A/D conversion section 2 and stored in a buffer memory 4 of a signal processing section 3 only for a prescribed tine and sent to a modulation section 8. An input signal power calculation section 5 and an input signal zero cross number calculation section 6 calculate the number of times of zero crossings and the square sum (corresponding to signal power) of the date in the buffer memory 4 at every prescribed time. A switch control section 7 discriminates it as a voice period and silent period when the calculated value is a threshold level or above respectively and connects the transmission/ reception changeover switch 10 to the position of the transmission side while taking it as the voice input. Thus, the modulation signal outputted from a modulation section 8 passes through a transmission section 9 and a signal wave is transmitted from the antenna 11.
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