In Hulda's book, she states that you should zap at 355khz and 360khz for 3 minutes a day to zap the Herpes 2 virus specifically. So when I got my Zapper, I specifically ordered SmartKeys that would Zap at 355khz and 360khz. The Zapper itself does not allow you to program the unit to different frequencies, thats why you have to buy the pre-programmed SmartKeys. There are some other devices out that, that allows you to specifically zap at a certain frequency and they are around 300 bucks. Also, depending on what virus or bacteria you are trying to target, the zapping frequency will be different. Like zapping for Herpes 1 is a different frequency..