Asimple mono audio cable will work. Leave the power off on the slave and the power on with the instructor. The instructor holds trainer switch up to give control to student, let go of switch to take control back. Make sure both transmitters have the trim the same and when you give student control be flying straight and level at 50% throttle and make sure student has nutral controls and 50% throttle so the hand off to student is smooth. Also as mentioned in earlier thread I highly reccomend that you disable the ACT as described if you haven't already.