Well I spent about four hours tuning a multiple coil system to the point i was able to measure an output, when to my dismay i discovered a 1/8" peel and stick neo stuck to the bottom of one of my coils.When i removed the neo the whole system came out of tune and the output dropped to almost zero.This got me thinking about the TPU.Maybe the TPU is tuned with a magnet in place, and when he wanted to turn it off he just removed the magnet throwing it all out of tune..no reed switch needed :