Well, passing the TX back and forth is how they used to do it (with my Futaba Attack 4). If your TX doesn't have it, dont worry. It's a nice feature, but not necessary. If you pulled the crystal out of your TX and put it in your instructor's , he wouldn't have your trim settings, and when he trimmed out your plane on his TX, when you switched your crystals back, you'd have to retrim your personal TX. So best thing to do is to just leave the crystal alone and both you and the instructor use the same TX. Good luck! If I could do it, you can....