The PEMF coil was original designed for use with the Spooky Central. The SC powers the coil with a 29VDC 100 Hz signal. Thus, the coil using DC has polarity, and the BN side is to be used and is marked accordingly.
The PEMF coil's use on the generator directly was an after thought and request made by users here. Given that there is just enough power to drive the coil with the generator, an adapter was made to facilitate its use.
However, we run the PEMF coil with the full voltage and current the generator can muster. With the boost, this becomes +-20v and is typically ran using no offset, so the signal is AC. Meaning that the polarity of the coil will alternate. Hence, plugging into the MN or BN port is yields the same results.
The High Power output of the Spooky Boost is the same as the MN and BN ports, just with a different gender for the connector. Technically, it matches the BN port in terms of which output is wired to the center pin.
For more details, please check the link: