All electric jacks that I have seen can be operated manually.
When it comes to tongue jacks, there is something to consider. They come in two basic designs. A top mounted motor ie: Atwood or a side mounted motor ie; Barker, Ultrafab, Husky and the rest.
The top motor mount design is the same as a manual jack as far as that operation goes.
The side mounted jacks are different, and the difference can be a problem.
The emergency handle inserts into the roof of the housing, and is cranked on a horizontal plane. This can cause interference with the propane tanks, making the operation a real pain. You can only turn it half a revolution, then must remove the handle, turn it 180 degrees, reinsert it and repeat this many times. I found this out the hard way when a Ultrafab on my new TT failed when hitching it up for the first time at the dealers lot.... I only owned that jack for 20-30 minutes. The dealer agreed with me on the stupidity of the design, and gave me full credit towards an Atwood.
This may not be an issue for all TTs because of differing designs... But it for sure won't be an issue with the Atwood.