| 摘要 |
Power sourcing equipment comprising: a power input; an output port; a control circuit comprising a means for sensing that a voltage component of power received at the power input is above a pre-determined threshold; a non-uniform signal source; an impedance associated with the non-uniform signal source; and an electronically controlled switch responsive to the control circuit, the electronically controlled switch being arranged to switchably operatively connect the impedance to at least momentarily be seen across the output port; the control circuit being operative responsive to an output of the means for sensing to operatively connect the impedance via the operation of the electronically controlled switch; the electronically controlled switch being operative to disconnect the impedance from being seen across the output port in the absence of the indicative output.
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