| 摘要 |
The invention relates to a two-channel unit (1) with input-side digital signaling stages (MS0-MS7) for a safety device which is operated in the safe mode, having two controllers (2a, 2b) which can be controlled by a higher-level safe computer and are each connected to an input (4) and to an output (3) of the signaling stages (MS0-MS7) which have two channels, having a test circuit (5) which sets all of the inputs of the signaling stages (MS0-MS7) to a defined state in order to test the signaling stages (MS0-MS7) controlled by the controllers (2a, 2b) with simulated input signals then being passed from the two controllers (2a, 2b) to the inputs (4), and the output signals produced in this way being recorded and being made available to the higher-level computer, with the controllers (2a, 2b) and the computer communicating with one another via independent serial buses (6) which are separate from one another, each serial bus (6) having potential isolation (6a), and optocouplers being used for potential isolation (6a) in the serial buses (6). In order to ensure potential isolation by means of optocouplers even in the event of a fault, it is proposed that power loss limiting be provided for the optocouplers.
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