General Definitions: Notes
Data Link Cable - The data link cable consists of a twisted pair of insulated data wires that are covered by a metallized foil shield with a drain wire and are enclosed under an insulating jacket. The data link cable meets the SAE-specified characteristic impedance of 120 ohms. Maintaining this impedance level by the use of proper materials and procedures is critical to the integrity of the data signal. Never splice "regular" automotive wire (such as GXL, SXL, TXL) into the data link cable.
Data Wires - Data wires refer to insulated copper conductors. In contrast, the data link cable refers to the entire package of data wires, metallized foil shield, and drain wire, all under a common insulating jacket. The data wires are green and yellow. The yellow wire is referred to as CAN_H and the green wire is CAN_L in SAE J1939/11.
Backbone - The backbone is the main part of the cable. This section of cable is terminated at each end with a resistor.
Stubs - Stubs are short lengths of data link cable from the backbone to electronic control units (ECUs).
Fig 1 shows a schematic of atypical communications and control system.