| 摘要 |
A control station (8) is coupled to a plurality of tributary devices (16, 18 , 20) by way of at least one high speed broadcast downstream data channel (9) and more than one shared lower speed upstream data channels (11, 13). The control station (8) broadcasts data to all the tributary devices (10, 16, 18 ) and selects a channel for a specific tributary device (16, 18, 20) to respon d to a poll. After polling, the tributary device (10, 16, 18) changes the tributary device transmitter (42) to the frequency of the selected channel. The tributary device (16, 18, 20) either sends data to send to the control station (8) or sends a negative acknowledge to the control station (8). If a negative acknowledgment was transmitted, the control station (8) notifies th e control station transmitter (10) that the channel is idle.
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