| 摘要 |
PURPOSE:To transfer specific information urgently by forcibly receiving images over a spot channel with a down signal from a center without reference to the in-use state of a terminal unit and by making sure that information transfer has been done securely. CONSTITUTION:In the CATV system that tansmits various television programs from one center 4 to television receivers 3 provided to respective terminal units 35 through wire by connecting one center 4 to many terminal units 35 via cable 5, down data for flowing spot information are transmitted from data transmitter 28 in center 4 to main box 33 of each terminal unit 35. The down data are inputted to the communication controller via the down data receiver to operate the channel converter, thereby changing television receiver 3 from another channel over to the spot channel forcibly. The down data contains data showing that an answer is required, and through the operation of the answer button by a viewer, the center answers by an up data signal. |
