Okay, now I have discovered that when I plugged a Kodak Ektagraphic programmable dissolve control, model 2, into the RT-300, the projector advances slides continuously. It just keeps cycling the tray around. The dissolve control doesn't even have to be turned on! When I plug in my Entre three-projector dissolve control, everything works normally. I can even run one Ektagraphic and one RT-300, no problem at all. But strangely, the control that Kodak makes is apparently not compatible. Anyone else ever run into this?