The last transformer was 110 vac, which is what you want. Almost all of the earlier transformers were 220 vac. Keith is right - if you hook the 220 v transformer to 110/120, you are going to get about 6 v out. If you happen to have 240v outlets wired in your house, you will be fine, but most outlets are only 120.
Why do I keep bouncing between 110, 120, 220, and 240?
Technically in the U.S. we run 240 volt single phase to most homes, but by using a center tapped transformer and hooking the center to neutral/ground at the pole, we basically have 120v outlets (hot to neutral). Depending on where you live, it's not uncommon to see the voltage sag to 115. 110 is a little on the low side for the U.S., but not uncommon in other countries. In any case, 110 and 120 are close enough that most stuff won't notice...
220 and 240 is basically the same idea. 208 however is usually associated with 3 phase power - usually installed in commercial buildings.