stibitz.adder

For the heck of it, I've tried to design an electro-mechanical binary adder that can automatically do the carry of the one that arises in 1 + 1 = 10. Of course, you reply, "George Stibitz's already did that in 1937 as you see here..." http://www.toronto-montessori.on.ca/bsutherland/electricity/stibitz.html But hey: this is retrocomputing, after all, and I'm not trying to duplicate Stibitz--my aim is to come up with an electro-mechanical binary adder architecture that's even simpler than his 2 switches, 2 bulbs, 2 batteries, and 2 relays version. I think I've done it using 3 switches, 4 bulbs, and 1 battery. Yes, still eight components but because it lacks the relays, I think it's definitely simpler and therefore a kind of retro-breakthrough. And yes, mine does carry the one for 1 + 1 = 10. Feel free to try building this (or better it if you can with even fewer components). But I do have a stupid question for everyone that exposes the holes in my education: if my adder can successfully do all of the below calculations but no more 0 + 0 = 0 0 + 1 = 1 0 + 10 = 10 0 + 11 = 11 1 + 0 = 1 1 + 1 = 10 1 + 10 = 11 10 + 0 = 10 10 + 1 = 11 11 + 0 = 11 have I constructed a 1-bit binary adder or a 2-bit binary adder? Thanks, S.F. Hall