J1939/14 specifies one of three possible physical layers for a J1939 network. This specification is responsible for defining things such as backbone length, stub length, network termination, twists per inch, shielding, shielding termination, baud rate, and signal slew rate.

Besides the above mentioned parameters there are several other details such as connector dimensions and testing requirements specified by this standard. For complete information, we recommend buying the specification from the SAE when it becomes available.