| 摘要 |
PURPOSE: To improve response of a service even if a wide frequency band is not used by setting up mutually independent two-way communication channels on the upstream side and the downstream side by the use of a sub-information station arranged on the way of a communication line. CONSTITUTION: At least one sub-information station is arranged on the way of a communication line. The sub-information station includes a 1st two-way communication channel for executing two-way information service communication only with the upstream direction in an UP signal frequency band and sets up a 2nd two-way communication channel for executing two-way information service communication only with the downstream side in a DOWN signal frequency band. In this case, a 1st channel signal and a 2nd channel signal are mutually independently band-stopped by respective band rejection filters 45, 48 so as not to be leaked respectively to the downstream side and the upstream side. Information data obtained through the 1st and 2nd channels are stored in a storage means 63 in the sub-information station so as to be shared and necessary information are properly supplied in accordance with a request from the upstream side or the downstream side.
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