Query on Nixie clock circuit operation

摘要

I'd like to ask a question in regards to the Retro Nixie Clock PSU published in the February & March 2015 issues of Silicon Chip. On your circuit diagram on page 28 of the February issue, there is nothing connected to the pin 2 (SE) of REGl, essentially leaving the internal transistor's emitter floating. Can you please clarify how and why it works then?