Two frequency selection:
30000 Hz for zapping
1000 Hz for zappicating
Two program selection:
Think about creating the accessories Hulda recommends for any zapper.
Plates for plate zapping
Regarding your question why Hulda selects 30000 Hz quote from the syncrometer manual page 81
“When a high frequency ac voltage was applied to a human, using hand electrodes, and the current flow measured, it could be seen that the higher the frequency (from zero up), the greater the current. Obviously, the body capacitors were coming into play.
But at about 30,000 cycles per second the current began to decline, showing the resistance was now increasing. The explanations were only speculative: such as “skin effect”, saturation of the capacitors, inductors coming into play, and others.
For this reason a frequency of about 30 KHz (30,000 cycles per second) was chosen for the zapper. But other frequencies may prove to have special value as research progresses.
As the user parazapper explained in his own words "Dr. Clark chose 30 kHz, simply because it passes more current than lower frequencies do. I agree with this as the 30 kHz has a stronger signal at the higher frequencies"