| 摘要 |
PURPOSE:To improve the utilization efficiency of a transmission line and to facilitate demodulation by measuring timing by a center device. CONSTITUTION:A response signal RSPi from a terminal device is supplied to a timing measuring circuit 15, which discriminates its identification code and measures the difference between reception timing and reference timing. The time of the measured difference is sent to a corresponding line concentration and distribution terminal MAU 3 as the correction time of transmission timing of the signal RSPi. A transmission timing generator 39 controls the transmission timing of a subframe and the transmission timing of the signal RSPi and informs a frame synthesizing circuit 47 of that. Thus, the timing is measured by the center device to eliminate the need to return the signal RSP to a down ring, so the utilization efficiency of the transmission line is improved.
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