Slave always has power off, even with computer radio, or so I was taught and every buddy box system I have read up on indicates.

The power "comes on" when you plug in the trainer cord, (at least mine does, all three radios I have work this way) but it does not power up the transmitter RF circuitry. So your computer control system is then on, and ready to interface with the master radio's transmiter circuit, but you arent sending an extra RF signal out to screw someone elses day up.

I plug in the following order:

1: Master TX turned on range checked etc. Take aircraft off and get it ready for student pilot. (If student is doingtakeoffs, then once range check is done proceed to step 2)
2: Student plugs into his box, power switch OFF, and then into the master while the instructor maintains positive control of the aircraft. (Actually we've done this in both sequences, the slave then master and master then slave, it doesnt seem to matter with my outfit)
3: When the student and the instructor are ready, (hopefully) the instructor pulls the trainer switch and it all works..