From left to right: 1 is the live wire input, which flows out of the live wire of the electric appliance from 2 through the current coil, and then connects to the electric meters 3 and 4 through the zero line of the electric appliance. So 1 2 is connected, and the resistance is very small;

The live wire is input from 1, passes through the voltage coil, and flows out from 3 to the zero line, so it is also connected, but the resistance is very large;

3, 4 directly connected to the zero line, no resistance.