One thing to be aware of if you use the 662 as the master. The button you refer to is tricky. It is hard to hold for any length of time and on mine, just a slight roll of the finger/thumb holding it down can revert control back to the student. My instructor and I used my 662 as a master during my training and we can attribute at least 3 instances where the instructor thought I had the plane, but his thumb had rolled a little bit and it was me that had the plane and didn't know it. One other problem, it is very difficult to hold the button down and keep the throttle semi-equal to the one on the slave. We got through my training and I love the radio, just be real CAREFUL using it as the master. IMHO.