In a buddy box, the Master box is the ONLY one transmitting.[8D] thus it is the only one that needs to be turned on.Some people even( due to superstition or disbelief)[X(] pull the crystal out of the student boxs. At our club, the Buddy Boxes dont even have antennas or batteries. The only portion of the Student box that is functiona is the Controls, they are "jumpered" as it were, by actuating the Trainer button on the Master box. So therefore,(correct me if Im wrong, which has been known to happen). The Student is in control until the Instructor releases the trainer switch, and doesnt recieve control until the trainer switch is depressed again. Futaba 9Cs and up Take it a step further and allow the trainer to designate what controls the student has. But thats another thread Im sure. My club has 5 instructor qualified flyers, they have trainer night every thursday night in good weather and usually at least 2 of them are there. They use the buddy boxes exclusively as the method of instruction, I took my first flight on one and 6 subsequent flights to get the basics. It was invaluable, I now have two of the three style buddy cords in my TX box, should the need ever arise for someone to buddy box (particularly me on a new plane) Its not unusual to see 4 pilot stations occupied by 8 people on trainer night,,,great for learning traffic flying