In FrameMaker 2015 I cannot find the option to prevent me from entering two spaces after a period. Sure I can get the spell check to fix it afterwards but there was an option previously to convert those double spaces to single spaces while I type. I think this also worked in the middle of a sentence too.
This is a document specific setting. Open the document and go to > Format > Document > Text Options...The "Text Options" Dialog appears. Select "Smart Spaces" and click "Apply". FrameMaker will now prevent you from typing in two normal spaces after each other:Please note that this does not protect you from e.g. inserting two spaces via Find/Change.