| 摘要 |
A filter arrangement (FA) particularly adapted to be used in a "splitter" (SP1) of an ADSL system where several POTS equipments (POTS1-POTS3), e.g. subscriber sets, are connected to a same telecommunication line (TP). The arrangement, located at the customer premises (CP), includes for each POTS equipment a distinct low-pass filter circuit (LP; LP1-3) to separate low frequency POTS signals from high frequency ADSL signals simultaneously transmitted over the same copper twisted-pair telecommunication line (TP). Each low-pass filter circuit is provided with a current sensing circuit (SC), e.g. an electrical relay, that activates a switch (SW) when the current flowing through the filter exceeds a predetermined value. Since several high order filter circuits can not be put in parallel, mainly because their capacitive values will then add, the present filter circuit is basically a 1st order filter that comprises the series connection of two transformers (T1, T2) separated by the coil of the relay. When the current increases, i.e. because the associated subscriber set goes off-hook, the switch activated by the relay inserts a capacitor across the line and between the two transformers. The filter circuit becomes then a 3rd order filter that is constituted by the cascade connection of the first transformer (T1), the capacitor (C) and the second transformer (T2). Since the order to the other filters circuits of the arrangement is not changed, there is no mutual disturbance.
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