The so-called main line refers to the two main wires between the main power supply and all electrical appliances. The main wire must be made of coarse copper core wire, as it carries the charge of various electrical appliances and requires high-performance coarse copper wire. The bypass can choose multi-core wires.

A wire is composed of one or several flexible wires, wrapped with a light and soft protective layer; A cable is composed of one or several insulated wires, with a tough outer layer made of metal or rubber. Good quality wires are generally within the specified weight range. The commonly used plastic insulated single stranded copper core wire with a cross-sectional area of 1.5 has a weight of 1.8-1.9kg per 100m; 2.5 plastic insulated single stranded copper core wire, weighing 2.8-3.0kg per 100m; 4.0 plastic insulated single stranded copper core wire, with a weight of 4.1-4.2kg per 100m, etc. Poor quality wires have insufficient weight, either insufficient length, or excessive impurities in the copper core of the wires.