Many terms used in this Standard are defined in previous IRE Standardsfl], including: Bobbin Core. A tape-wound core in which the ferromagnetic tape has been wrapped on a form or bobbin which supplies mechanical support to the tape.B. Methods of Measurement The electrical characteristics of bobbin cores are ordinarily measured by applying one or more tests chosen from one of two categories of test methods, These categories are presented below as the open-circuit test and the integrated-output test. Each of these methods is a valid and useful test, but the methods are basically different and should not be expected to give the same test results. In each method, the number of turns, amperes and seconds are to be specified for particular cases.