What I'm getting in my terminal window contains some correct characters, but mostly gibberish. The appearance of some correct characters means I'm connected, but clearly I've set something incorrectly ...

I'm looking at getting a used Digi CM16 serial console off ebay to put in a remote location. It comes with RJ45 ports rather than DB9. The devices it's going to connect to also use RJ45 (APC PDUs, ...