I have this 2.5VA Split-Bobbin Power Transformer 115/230VAC. According to page 3 of the Data Sheet (PDF) it looks like there is a line on the "DSW" version on the pin 1-4 side. This seems to correspond to a small step down (maybe 1-2 mm or so) on the top of the physical transformer.
Is it safe to assume that is the identifier for the pin 1-4 side? If not, how do I identify which side is the input and which side is the output?