What is a slip ring? Is it electrical? Guess what. I used an MRC Power pack to make my controller when my crane was tethered! It works well. That's basically the circuit I copied in making up these parts lists, and a controller that is used in my upper unit.
I put my paddle switches in the MRC box, and wired them to a cat 5 phone jack. That only allows for 4 functions though, just the upper unit. I still plan to use it on another project. The ammeter on the right unplugs and pulls out. The pack can also be hooked up to a battery pack so plugging it in is optional. Handy at shows.
Spaghetti, anyone?
Cat 5 plug keeps it clean. The power cord was cut down to just the plug, too. No cord to drag around when its hooked up to the battery pack.