To provide with respect a short-distance subscriber with a subscriber line interface device and a method with low power consumption and lower power supply capacity.

The subscriber line interface device is provided with a DC voltage variable feedback DC-DC converter power supply 19, between a power terminal 6 for feeding the short-distance subscriber of a feed circuit 4 and an external DC power supply 21 in off-hook of the short-distance subscriber, and the DC voltage variable feedback DC-DC converter power supply 19 generates DC voltage (VSB) which follows external DC power supply voltage (VBB). The DC voltage variable feedback DC-DC converter power supply 19 switches the current which flows to the short-distance subscriber, by a switching element 15 in the off-hook of the short-distance subscriber and feeds converted power by the switching operation back to the DC power supply 21.

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