Datacraft Quadcraft - Industrial class modem from the late 1980’s. They supported a Hayes AT command set and an X-series command set (though I can’t remember which). If I ever find the manual in my things, I’ll update the details. They also supported MNP2-4 Error correction, as well as fixed-rate serial speeds. I used to run them at 4800 bps on the serial and turned the buffer size down to 64 bytes, which improved latency for users on the BBS I ran.
They had a massive 23 LEDs on the front panel! At one point, I had 4 of these things, plus 4 other modems (2x USR Dual Standard V34bis & 2x Netcomm Trailblazers), plus a 486 PC, all in my bedroom about 10 feet from my bed. I have no idea how I managed to sleep through all that!
And yes, it still works! Configured in the default mode that I had them in still (Auto Answer). I haven’t hooked it up to a serial terminal yet, but I really expect it’ll just work fine. I’ve got 3 of these (used to have 4).
Edited to add: I should note that all the larger function LEDs on the right side (12 of them) are actually fronted by membrane buttons. You could push these to toggle/switch to that setting.
Sorry about the slightly fuzzy pic, but as you can see, no large electrolytic caps that could fail over time, plus being this old, my guess is they’re still going to be rock solid (none of this garbage import electrolyte).
You can tell these were an Industrial modem. Screw terminals for all the line connections on the back and options for 2 or 4 wire leased line modes. The right PRG/PERM switch is unpopulated, but was obviously a thing. There’s 2x 8pin dip switches on the lower board (just out of shot), and I remember one of them did allow you to lock out saving of programming, so I suspect it was just in parallel with that dip switch. There’s a bunch of jumpers and dip switches on the top board, but I remember that these weren’t in the manual, so I suspect these were for various add-on options or product differences. Power supply was 18VAC Centre tapped, provided on the big barrel connector in the back. In the centre of the heatsink was an LM309K voltage regulator.
Edited to add: One further note. There were a few models similar to this. There was a less-functional 2400bps model that didn’t do Error correction or the like (can’t remember what it was called, but it was the same case with a few less function LEDs on the front), and there was also the Quincraft, which was basically the same as the Quadraft, but it did V.32 9600bps as well. I never had either of those, but knew they existed.