Can someone elaborate on why you'd want the 120v switch? I must be missing something. Seems to me if you want 120v, just don't use this device at all...
Well, I use it for testing. There are a lot of possible uses, one is that it can be used on only one outlet in 120v mode, so it allows the same unit to double as a 8 foot long 120v adapter in the event you can't find 2 non GFCI circuits.
Scenario: You get your "Easy240" out, search for plugs, but cannot locate 2 on opposing circuits, so you simply throw the switch to 120v and not have to deal with another trip to the trunk to retrieve the 120v adapter.
Another: You are plugged into 2 circuits in your kitchen, but your wife wants to make you some toast and cord #2 is sharing the outlet with the toaster. Rather than unplug your car completely, she can simply switch the toggle over and the car will continue charging on 120v while your toast is being made. Then when she is done, she can kick it back to 240v. The car will never stop charging, and you won't have to go reset anything.