Magnetic cores of types: OL 25 / 40-10, OL 20 / 32-10, OL32 / 50-16 from permalloy 79 NM 0.1 for the frequency range up to 0.5 MHz. Magnetic cores of types: OL 16 / 26-6.5, OL 40 / 64-25, OL64 / 100-40 from low-frequency electrical steel 3422-0.08, 3413-0.35, 3412-0.35 for the frequency range up to 1 kHz. The number and types of windings, as well as the number of turns and the transformation ratio, are at the request of the consumer.