Chuck, AE4CW (what a nice call) demonstrating the North Fulton Amateur Radio League's "Power Gate" kit.  You hook up your power supply and a backup battery  to your rig and the "gate" choses the source with the highest voltage to supply power to your rig.  That way you can get an automtic battery back up if the power goes out on the power supply.  You can also hook up 2 batteries to your rig and have the "gate" switch to a new battery when the first one gets too low.  There is more info on this kit on the NFARL web site at: