| 摘要 |
<p>In a cable television network time division multiplexed signalling is used between a distribution centre (1) and customer termination units (5) by way of e.g. a ''tree and branch'' network (4). Each termination unit (5) is allocated a group address and a unit address. The termination units (5) are each polled in a slow track scan by forwarding of a group address, the units (5) responding in turn to provide an indication of status. If the status indicates that an activity request has been made the terminal is allocated a channel for fast track scanning. The distribution centre (1) scans each group of terminals (5) in turn and between adjacent group scans addresses active terminals. Data channel occupancy by inactive terminals is thus avoided.</p> |
