Transistors and Mosfets don't provide enough isolation. I am running 1 to 4 cameras per controller and focus as well as shutter lines for each camera. Each camera has to be isolated from the other cameras or you get strange interactions and possible feedback of voltage for any of the cameras connected. I have tried it with transistors and not had great results. I have heard lots of good stories about frying of cameras when not properly isolated. Anyway any ideas on low current optoisolators? I have a few more things to try this week.