If you've never seen a matrix switch before, it looks like just a bunch of slidey things. Isn't that fun? They can even be put into pretty patterns!
Really though, they're for connecting circuits. They were used in the ARP 2500 Synthesizer (which is quite fun to use if you're ever given the opportunity). From another piece of equipment of the same era comes today's picture of the day.
800x600 (75 KB) · gallery page
Yes, kamoranakrre is guilty of arranging the sliders into the pattern you see here. And why not?