| 摘要 |
A device for intrinsically safe DC power supply of a data or telephony transmission system operating with RF carriers is to be indicated in which LC filters for specific frequency ranges are inserted between the lines feeding the output of a DC supply unit which satisfies stringent requirements for intrinsic safety in the presence of highly explosive gases (ethylene). This object is achieved by disposing an electronic switch (1) between the lines (2, 3) feeding the filter and, when a short circuit occurs, or an open circuit following a short circuit, a positive pulse is generated in a differentiator (4) and fed via a timer (5) to a connector (6) controlling the switch (1) with the capacity to close the switch during the output signal of the timer (5) and thereafter to open it with a linear time pattern. The preferred field of application is mining. <IMAGE>
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