Hi,
I may have found a mistake with a ladder circuit diagram.
This page:
http://www.allaboutcircuits.com/vol_4/chpt_9/3.html
About a third of the way down...
I "think" the ladder logic for the two half adders is incorrect. C1 and C2 are shown wired in series instead of parallel.
See attached graphic for details.

Hope I'm not being a nuisance. I'm a huge fan of this site and want to help give back anyway I can.
Thanks,
- Randy

 

You are not a nuisance at all. You are actively helping us improve our favourite site and we thank you for that.

I 'm not very familiar with ladder logic, but in the circuit the two carries of the half-adders are ORed together and I, too, believe that calls for a parallel connection in the ladder diagram.