Patchbay
A panel where every input and output in the studio ends up on a socket, so signal paths can be changed with a short cable instead of someone crawling behind the rack.
Sockets come in pairs, output above input. If a pair is normalled, the signal passes straight through when nothing is plugged in — from a console's insert send to a compressor, say. Half-normalled additionally lets you take a parallel feed without breaking the connection. The conventions are what make a patchbay useful, and what turn a badly labelled one into an evening of troubleshooting.
The small TT or Bantam plugs come from telephone exchanges, where the same principle connected calls by hand. As outboard gear gave way to plugins, patchbays shrank, but the idea lives on in software: audio interface routing apps and the graph in JACK or PipeWire are patchbays without the cables.