It's for a Tandy 1000.
"Expand your Tandy 1000's storage affordably. Add two to the
Tandy 1000 or one to the Tandy 1000 HD for 40 megabytes of
total system storage (Cable Kit and installation required for
secondary unit). Requires Hard Disk Controller Board.
25-1041 699.00 "
If you don't want to make your own cable, these work great and aren't expensive: https://www.8bitclassics.com/product/trs-80-model-i-to-composite-video-cable/
The requirements are unusual - five different voltages! I'd like to use a modern power supply (Mean Well or similar) for the +5/+12v, but it would need a circuit to generate the +8/+16/-16v. I'd love to find that someone's already done that work so I don't have to.
From the Z-100 Technical...
Thanks for the tips, but for no good reason I really want to have a M4 on my home network. Based on the research I've done, it looks like a M3SE is the easiest way to do that?
I'm looking at picking up a Model 4 that may or may not have working floppies. Since there are now auto-boot EPROMs available for the M3SE, does that mean that I'd be able to get things running as-is and worry about fixing the floppies some other day?
Thanks!