Single-wire system and negative grounding There are two important concepts in the vehicle grounding system: single-wire system and negative grounding. The single-wire system refers to the use of only one wire to connect from the power supply to the electrical equipment in the automotive electronic system, and the metal body such as the car body, chassis, and engine is used as another common wire. Since the single-wire system saves wires, the lines are simplified and clear, the installation and maintenance are convenient, and the electrical devices do not need to be insulated from the vehicle body, so the single-wire system is generally used in modern automotive electrical systems. When the vehicle electrical system adopts a single-wire system, one electrode of the battery is connected to the vehicle body, commonly known as “grounding”. If the negative electrode of the battery is connected to the car body, it is called the negative electrode grounding, otherwise it is the positive electrode grounding. According to national standards, the electrical systems of domestic automobiles are all grounded negatively.