Gives characteristics, ratings and inspection requirements for magnetic cores of assessed quality. Such cores, intended for inductors and transformers in tuned circuits for professional and industrial applications, consist of at least two parts forming a substantially closed magnetic circuit. It selects from generic specification CECC 25000, appropriate methods of test and contains test schedules to be used in detail specifications derived from this specification. Each test schedule, referenced by a CECC number forms a blank detail specification. The cores may be used with an adjuster which allows change of inductance for tuning. BS AMD 7577 RENUMBERS THIS STANDARD TO BS EN 125100