An outlet (1) includes a plurality of blade receiving members (13) adapted in use to be connected respectively to a plurality of DC supply lines (Wdc1 and Wdc2), and to be connected respectively to a plurality of blades (21) of an outlet plug (2). The outlet (1) is configured to supply DC power from the plurality of the DC supply lines (Wdc1 and Wdc2) to the outlet plug (2) via the plurality of the blade receiving members (13). The outlet (1) includes a wiring detecting means (3). The wiring detecting means (3) is configured to determine proper wiring when the plurality of the DC supply lines is connected respectively to the plurality of the blade receiving members at proper polarity, and to determine improper wiring when the plurality of the DC supply lines is connected respectively to the plurality of the blade receiving members at improper polarity.