Control: How to solve the punchcard terminal puzzle
Most of the gameplay in Control is driven by combat and exploration, but there are a few puzzles to solve along the way too. One such puzzle along the game's critical story path pops up in the HRA Lab, while you're on the "Old Boy's Club" mission. The mission directive is to "restart the punchcard terminals" in order to activate the HRA machine - but you might run into a bit of trouble solving what seems like it should be a simple puzzle at first.
Punchcards and terminals
The first step in solving the puzzle is to gather the punchcards scattered around the immediate area. They aren't hard to find - they are yellow rectangles with black symbols on them, and aside from the terminals themselves they are the only things around that will display Control's helpful "you can interact with this item" visual blip.
Four of the punchcards are around the machine itself, while the fifth is up the stairs you'll find in the back corner of the room. These take you up to an area with the fourth terminal, as well as an additional white board of notes which you'll need to give you the clues to solve the puzzle yourself.
Once you have all five punchcards, you need to use the clues in your environment to determine which one goes into which terminal machine. The terminals are clearly labeled from one through five, and you have five punchcards - so putting them in the right order will allow you to turn the machine on and make progress. The only tricky thing about the terminals themselves is to note that 1, 2, 3, and 5 are down in the main chamber, while 4 is up in the yellow room.
Making sense the whiteboards
We need a way to refer to the symbols for this guide, so I've added letter labels here:
The information you need to solve this puzzle is displayed on the three whiteboards in the area - two downstairs, and one upstairs. These whiteboards show sequences of symbols that didn't work for the researcher previously working in the HRA lab, with the misplaced or incorrect symbols crossed out in red.
To make it easier, here are all three white boards in a single image:
Comparing these images, we can pretty easily determine that A goes in terminal 1, E and C look to go in terminals 2 and 3, respectively, B goes in 4, and D goes in 5. But if you try the cards in that order in the terminals, then attempt to activate the machine...it doesn't work.
Why doesn't it work?
If you're reading this guide you probably missed the same detail that I did, and might have thought that the problem had something to do with 4 and 5, because they are the only ones that seem to take a little deduction to figure out. But the key piece of information you need is written on one of the whiteboards itself, the one in the top left of the image above. There, the researcher has written "CHANGING VARIABLES" with arrows pointing to the symbols in the 2 and 3 position.
It's easy to overlook this since none of the other written notes on the boards are that important, and might actually be hard to see depending on your screen resolution and brightness. But what it's telling you is that you have to swap the symbols in the 2 and 3 positions in order to solve the puzzle. So the final sequence, based on our letter notation above, should go: A-C-E-B-D, in that order in the different terminals.
If a picture is more helpful, put them in the terminals like this:
Insert each card in its corresponding terminal and leave it there. Once they are all in the terminals in the right order, you'll be able to activate the central machine and move on with the mission.