5.1.2 Configuration of equipment under test (EUT) 5.1.2.1 Single connection to an a.c. mains supply Systems of interconnected equipment with individual connections to theAC MAINS SUPPLY shall have each piece of equipment tested separately. Systems of interconnected equipment with one common connection to the AC MAINS SUPPLY shall be treated as a single piece of equipment. See also 1.4.10 regarding the inclusion of optional features. NOTE Systems of interconnected equipment are specified in more detail in Annex A of IEC 60990. 5.1.2.2 Redundant multiple connections to an a.c. mains supply Equipment that is designed for multiple connections to theAC MAINS SUPPLY, only one of which is required at a time, shall be tested with only one connection. 5.1.2.3 Simultaneous multiple connections to an a.c. mains supply Equipment requiring power simultaneously from two or more AC MAINS SUPPLIESshall be tested with allAC MAINS SUPPLIES connected. The total TOUCH CURRENTthrough allPROTECTIVE EARTHING CONDUCTORS that are connected to each other and to earth is measured