I have a SynchroZap and am quite familiar with it. It is of the 30 kHz type ( she allowed a range of 27 kHz to 33 kHz although there were some models that used 35 kHz and even 36 kHz.
>- positive offset as all the Clark Zappers
You are wrong! Dr. Clark did not push the positive offset until after 1999. Actually it was first added to her books in 2002-2003.
The Article was published in 1998 and the study was actually done in 1996-1997.