PURPOSE: To cope with rise in the distribution voltage without replacement of the plug socket through replacement of the adaptor and alteration of extended wire and terminal connection.

CONSTITUTION: Bayonets 2 and 2' of a plug socket 1 adopt a polar arrangement after boosted in voltage while adaptors 6 and 7 are inserted into the plug socket in the polar layout varying with the distribution voltage. In operation, with the use of the adaptor 6, the load is fed with 100V before the boosting of voltage and with the use of the adaptor 7, the load 15 is fed with 200V. When the voltage is boosted to 230V, with the package connection of terminals 3c and 3d, a 230V power supply terminal is connected to plug socket terminals 3a to 3c. Then, after removal of the adaptors 6 and 7, a plug of 230V polar arrangement is inserted direct into the plug socket 1 to feed the load 19 with 230V.