| 摘要 |
A packet switched communications network comprises a controller ( 11 ) and a plurality of controlled units ( 12, 13, 14 ) arranged in a ring. Each of the controlled units comprises a switch ( 31 ) at its input, each switch including control means ( 44 ) that are responsive to control instructions transmitted by the controller ( 11 ). Depending on the instructions the switch ( 33 ) will either be configured to pass control instructions and data into or out of the controlled unit ( 12, 13, 14 ), or to forward the control instructions and data to a further controlled unit ( 12, 13, 14 ) that is connected to the controller ( 11 ) or back to the controller ( 11 ). In order for units in the ring, that are not registered with the controller ( 11 ), to acquire an address, the controller ( 11 ) transmits periodically broadcast packets, which contain a unique registration address to be used by an unregistered unit. Once registered, the unit can receive control instructions from the controller ( 11 ) as well as data.
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