Thanks for the help. I think I understand some of what you're saying. Before I get into voltages and other details, I need to see if I can even make this work at all in a way that I understand. I tried thinking about it with a transistor and still came up with no idea how to select a voltage into the correct cathode(s). The only way I can think to control a transistor is to ground the emitter leg which doesn't help me get voltage to the cathode of a two segment led block. Maybe that's why you mention a bipolar transistor, though I don't have any idea if .68v will light up a segment. Here's the diagram so far. I realize I'm omitting resistors on the anode sides of the segments and quite a bit more I'm sure. I just want to get the basic logic of how it might work right now.