More photos.

There are screw terminals marked by the arrow. You need to attach wires with proper voltage to them. You could use AT, ATX or custom power supply.

Simplest, but destructive (for power supply) way: use old ATX (or AT) power supply you don't care about and strip the wires. Match colors of wires. Insert them into screw terminals and clamp down with the screws. Don't use orange wires (don't mistake them with red or yellow). If there are multiple wires of same color, you can join them together.

"Proper" way: buy ATX to AT adapter cable and remove AT connectors, insert wires into terminal block. Congratulations, you converted that computer to ATX. You can also buy miniature 12V pico ATX power supply if you want to use something smaller.

Ideally you should check the voltages before turning everything on.

you wire AT power supply to the Block on the back where it indicate 12v 5v -5v etc

You should be grateful it has a dallas instead of some heinous barrel battery that leaked all over everything and destroyed it

Get crimp on open end eyelets and install them by crimping to the wires. Bare wires is good for testing.

Cheers,

Hey that's an Advantech PCA-6134 😀 I've got the later version of that from about '96. Get ready to desolder that Dallas to replace it or mod it with a battery, but that's great and reliable little board. Afaik you can power the board itself with a floppy connector from a PSU where you've got it always-on, but with mine it doesn't then power the ISA bus, so the video card didn't work.

Best to power the ISA backplane using those terminals. You don't need all of them to work, it should be okay with just 12v, 5v, gnd & -12v.

What were these things used for? Controlling machinery?

well anything that needed computer control somewhere, including machinery yes.