Automobile wiring terminals generally adopts single line system, parallel connection of electrical equipment, negative grounding and lines, which are distinguished with different color lines and numbers, and are divided into several main lines centered on the ignition switch.

1. Battery positive electrode wire: it is led out from the battery directly through the circuit breaker box, some directly from the battery positive wire into the starter positive wire column, and then from where to lead out the thinner positive wire into other circuits.
   

   
   

2. Ignition, instrument, indicator wire: circuit must be connected through car key.
   

   
   

3. Special line: no matter whether the engine is working or not, connecting appliances are required, such as receiving and discharging cigarette lighter, etc., are powered by a separate gear set by the ignition switch.
   

   
   

4. Starting control line: the control switch (contact) of the main circuit is usually disconnected by the magnetic switch. There are three wiring modes: the suction coil of low-power starter magnetic switch is controlled by the starting gear of the ignition switch; the suction coil of high-power starter is controlled by starter relay (such as Mitsubishi Heavy Vehicles); cars equipped with automatic transmission often connect the starting control line to the neutral switch in series to ensure neutral starting.
   

   
   

5. Grounding wire: Iron spots are distributed in the automobile body and form an electrode potential difference with different metals (such as iron, copper, aluminum, aluminum and iron). Some iron parts are prone to contamination or corrosion by mud or oil. Some iron parts are thin sheet metal, which may lead to poor iron, such as lights not work, instruments not work, and horns not ring, etc. Therefore, some automobile terminals use double iron wires.