Thanks Quiz (at # 23). It was the use of "bits" for I and O that held me back. I have not seen that indication used before.
I enjoyed this puzzle, although I have to agree with others that it was not as difficult as some other Listeners. However, I think that criticism of the setter is unwarranted. Without them, we would have no puzzles to solve. I would say to those who have been critical, why not try to set one yourself. I have tried and it is unbelievably difficult. Remus must have spent many hours putting this one together.
Thanks Remus.