bryn, the control pattern is how your controls are set up. There are two different commonly used patterns, Cat or JD. On both control patterns, your left joystick controls the swing when moved left to right, and the right joystick dumps your bucket when moved to the right, and curls it in when you move it to the left. The difference is the fore and aft movement of the joysticks. On the Cat control pattern, when you move the left joystick forward, your dipper extends, and when you pull on it, it retracts. On the right control, pulling it back raises the main boom and shoving it forward lowers the boom. On the JD control pattern this is the opposite - The Right joystick extends the dipper when moved forward and pulls it in when you pull back. The Left lever raises the main boom when pulled and lowers it when pushed. Some guys have no problem switching between either control patterns but if you're like me it becomes problematic. If there are 2 or more guys who are used to running different control patterns you could have an issue, so somebody (obviously a lot smarter than me) came up with a control pattern switch so that Operator A who is used to Cat controls and Operator B who is used to JD controls can both use the machine using their preferred control pattern without having to re-plumb the hydraulic system. My Dad and I have this very issue, I'm used to the Cat pattern and he is used to the JD pattern, and when I bought my EX200 recently he insisted we install a control pattern switch so he could run it as well. Hope this helps. I'll see if I can find a diagram, or perhaps make one.
On second edit, here's a picture of the control pattern changer I built for my EX200. I used 2 valves but most small machines have the whole unit in 1 valve. As you can see there's quite a bit of plumbing going in and out, and physically undoing all the hoses and moving them around and then doing them back up just to suit different operators would be very time consuming and expensive.
