why would a potentiometer have 4 prongs, i thought it's meant to just have three? uk.rs-online.com/web/p/potentiometers/2633191

I've recently bought a house, and I've got a closet full of wiring I don't understand (it looks like they are splitting and recombining wires as well). Is a question (with pictures) asking "what is going on here" allowed?

I'm one of those "zero experience" guys, but I'm not trying to do my own electronics, just trying to figure out what is happening

@NathanMerrill are we talking mains wiring, or network/phone wiring? it sounds more like a DIY.SE question than an EE.SE question in either case

sorry, what's "mains"? Like power?

I'm pretty sure it's network/phone/some other signal thing

@NathanMerrill yeah, power

ok, I'll look into DIY. thanks

@barlop It's called a center tap

@barlop . . on page 361 of the data sheet you linked, it shows the fourth connection as a center tap (the schematic version).

don't worry, data sheet pages go from 359 to 371.