Dictating alphanumeric characters was a problem. For instance, I will dictate 'fone' and Jaya will look at me in bewilderment. After we developed the convention for spacebar, I started saying
'f one' which was easy to interpret as F1. In most cases Jaya will guess from the context that I mean the car race and not the key on the keyboard.
It is now easy to dictate something like H5N1. Of course, this is only when dictating to Jaya. People less schooled in the subtleties of communicating with me will write 'hfivenone' (assuming they get this far), which will lead to a lot of hair tugging in vain attempts to solve the conundrum before they throw in the towel with a 'let Jaya come'.