| 摘要 |
A system comprising a local site served by at least one remote site in digital logic communication therewith, the system further comprising mode selection logic including a hierarchy that prioritizes modes available at the local site. The hierarchical priority of a particular mode that may be selected at the local site or at any one of the remote sites determines the mode in which the local site will operate, further depending on the current mode selection state at other remote or local sites. A presently preferred embodiment of the invention is a valve actuator having three-way local mode selection capability (local/remote/off), where such mode control is additionally served by at least one remote site connected via a serial link to the local site of the actuator. In this exemplary embodiment, a hierarchy prioritizes these modes in the following order of high priority to low priority: (1) off; (2) local; (3) remote. Under the logic of the invention, if the "off" mode is selected at the local site or any one of the remote sites, then all the sites will behave in "off" mode. If the "local" mode is selected at the local site or any one of the remote sites, and no site is in "off" mode, then all the sites will behave in "local" mode. If the "remote" mode is selected at the local site and all of the remote sites, then all the sites will behave in "remote" mode.
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