The current transformer primary winding marks are P1 and P2, and the secondary winding marks are S1 and S2. If P1 and S1 are the same name, then this flag is called polarity reduction. The primary current flows from P1 and the secondary current flows from S1. The polarity check is very simple. In addition to checking on the transformer calibrator, DC test can also be used. Rollo Printer,Barcode Printer,Thermal Transfer Printer,Bluetooth Receipt Printer SUNLUX IOT Technology (Guangdong) INC. , https://www.sunluxbarcodereader.com