There are many factors that determine whether someone feels the contact frequencies...

The first is the frequencies themselves. Any over 10KHz should not be felt by anyone,only those less that 10K should resonate with nerves...

The second factor is the amplitude. We need a minimum of 14V to penetrate the skin and be effective, but can use up to 20 with the XM generator.

The third, is whether you are using the CS port or the Hi Pwr port on the Boost unit... The added resistor in the CS port circuit reduces any tingling so it generally isn’t bothersome.

Fourth, there is also a "Reduce Amplitude for Frequencies less than 10KHz in the software settings... If this is checked, it is also going to reduce the ability to sense the frequency...

Fifth, some people are not as sensitive as others and it is just not a problem for them...

Sixth, hydration levels have an effect on how easily the current flows within the body and can affect whether the signal is perceptible...

Seventh, you would not feel anything when you use Spooky Central contact mode. The TENS pads connected to the SC is a fixed 100 Hz ultrashort voltage spike of 320v, which is very high, but the duration of the pulse is extremely short. You will not feel it no matter what you try.

There may be others, but this should give you some idea...

Source: https://www.facebook.com/groups/spooky2/permalink/662004077294832/