I have a Zen Touch 2, a Cyclone Voyager and a Samsung galaxy Fame, all configured for USB debugging.
I also have a laptop running Ubuntu 12.04, the standard ADB obtained from apt-get, and Fastboot obtained from apt-get.
My problem is that when I plug in my Fame on it's own, I can see it in the list of attached devices when I run the adb devices command. However, when I attach the others, I cannot.
I have plugged them in on their own and tried all 4 different ports. Switching to PTP doesn't work. And it is not just the devices command.
How can I make them appear and allow me to use them?