The harness provides the overall of service equipment for a certain load source group, such as trunk line, switching device, control system, etc. The basic research content of traffic theory is to study the relationship among traffic, call loss and harness capacity. Therefore, harness is an important basic concept in traffic theory.

Basic composition:

1. It is convenient for installation and maintenance to ensure that the electrical equipment can work under the worst conditions. The wires of different specifications and colors used by the electrical equipment of the whole vehicle are integrated through reasonable arrangement, and the wires are bound into bundles with insulating materials, which is both complete and reliable.

2. Normal selection of wire cross-sectional area and color code

1) Correct selection of wire cross-sectional area

The electrical equipment on the vehicle selects the cross-sectional area of the wire used according to the load current. 60% of the actual current carrying capacity of wires can be selected for electrical equipment working for a long time; 60% - 100% of the actual current carrying capacity of wires can be used for electrical equipment working for a short time.

2) Selection of wire color code

In order to facilitate identification and maintenance, the wires in the wire harness adopt different colors.

For the convenience of marking in the circuit diagram, the colors of wires are represented by letters, and the colors represented are annotated in each circuit diagram.