JBK3 and JBK4 series machine‑tool control transformers are a new‑series product designed and manufactured with reference to the advanced technology of Siemens (Federal Republic of Germany) from the 1980s. They comply with relevant requirements of VDE0550, IEC204‑I, IEC439 and other standards. Suitable for AC 50 Hz‑60 Hz with input voltage not exceeding 500 V, they serve as general electrical control power supply, local lighting and indicator lamp power supply for various machine tools and mechanical equipment.