| 摘要 |
<P>PROBLEM TO BE SOLVED: To simplify a configuration of a receiving device in a center for a cable television transmission system. <P>SOLUTION: An optical signal transmitted through each optical transmission channel 10 directed to the center is changed into an electrical signal by each optoelectric transducer 12, and each up-signal changed into the electrical signal is combined into (n) groups ranging from a 1st group to a n-th group, and then mixed by a mixer 14s on a group-to-group basis. An output from the mixer 14 provided for every group is inputted into a demodulator 30 mounted in a rack 20 and provided for every group. An output signal from the demodulator 30 for each group is inputted into a center PC50. The center PC 50 issues a data-transmission enabling signal to the transmission channel by polling. A terminal which receives the transmission enabling signal transmits data if data to be transmitted exists. The up-signal is demodulated by a receiving device 30 for the group to which the transmission channel linked to the terminal which issues the signal belongs, and the center PC 50 receives data only from the receiving device 30. <P>COPYRIGHT: (C)2004,JPO |
