On the side you will find the single button that runs the whole Dr. Power II. It looks like a power button but it really isn't one. It's basically the "everything" button. You are either allowed to toggle between tests in Mode A, or have it cycle through the tests on its own with Mode B. It really isn't complicated if you glance at the help guide. There you will learn that less than a 5 second press and the device will cycle through each test in Mode A, whereas a hold for 5 seconds or more kicks it into Mode B, which cycles through the tests for you automatically. No rocket science here.