PURPOSE: To allow positive transmission of measurement data to any single phase two wires among single phase three wires by providing a load survey meter, a transmitter, and a switch means.

CONSTITUTION: Single phase two wires to be connected with the transfer section 36 of a load survey meter is switched by means of a switch 28. When the connection of a transmitter is switched after installation of a system due to some cause and the power supply for the transmitter is switched from one single phase two wires to another single phase two wires, for example, the switch 28 is turned to establish communication between the load survey meter and the transmitter thus allowing transmission of measurement data from the load survey mete to the transmitter. Since the switch 28 eliminates the need for fixing the single phase two wires onto which the carrier from the carrier section 36 of load survey meter is superposed, the installation work is simplified and highly reliable communication is realized.