RML LINK 480Z with network connection

I've just acquired another 480Z, but this one powers up with the words "Z-NET Firmware Vers 1.1q", and there is a BNC connector on the back. Would I be right in thinking that this is a Research Machines proprietary network? The other good news is that I've got a working 5.25" disk drive with it, and a single disk, for an educational Viking game. (I thought that the machine dated from 1984, but perhaps I'm a thousand years out). Instead of typing "R" to run BASIC from ROM, you can type "B", and it boots CP/M then exit the game and use CP/M, which is something I've not done for 15 years. Oddly enough, the 480Z talks to the disk drive through the serial port. The disk drive also contains another serial port, which I've yet to experiment with. As with my other 480Z, the high resolution graphics only displays in black and white on a television. I've still not made up a monitor cable, despite asking for (and getting) the TTL RGB pinouts many months ago, so I don't know whether it will produce a colour display at all.