Thanks , that pretty much explains it. Transmitted signal goes to the reciever and changed to a common servo input signal not needing a set crystal and drives the servo. Always wondered about that I knew the two crystals had to match. Now if I could just keep the idle trim set on my beat up trainner. Still quits upon throttle closeing. Even the pros at the field have set it but still no good. One thing, getting profecient with dead stick landings. gphil