The electrical measuring instrument auxiliaries covered by this specification are intended for general use to extend the scale range of measuring instruments or to provide low current for relay circuits. Shunts and current transformer are for use in current circuits to extend their scale ranges. Resistors and potential transformers are for use in potential circuits to extend their scale ranges. Current transformers for relay service provide low current for relay circuits. Current transformer protective devices protect the secondary side of current transformers against excess voltage.