Once upon a time (circa 1999), RS232 was the primary mechanism for communicating and updating firmware in most computer systems. This means that we had to make a bunch of cables and rather than soldering pin the techie crew often used these modular adapters as the pinout needed for various installations varied.
ADM 9F8 GR - RJ45 to db9 fem The following is for the D-Sub-RJ-45 Modular Adapter
1 - blu 2 - org 3 - blk 4 - red 5 - grn 6 - yel 7 - brn 8 - wht