Most modern DSO's don't have Alternate Triggering, but Dave shows you how to do it anyway! This allows you to trigger on, align, view and anaylse two otherwise asynchronous time un-correlated signals on the screen at once. Also a look at Dual Time Base oscilloscopes.
Oscilloscope Tutorial Video Playlist: https://www.youtube.com/playlist?list=PLvOlSehNtuHsCTtj-T_vkpTTbBXW4sB51