When using contact mode, it doesn't matter which goes to what point, only that both are connected to make a complete circuit.
Any frequency is going to cycle positive and neutral, positive to negative, or neutral to negative. All are going to work. It is the frequency that causes the vibration of the pathogen, etc. So there MUST be transitions to achieve this. The difference is that both portions of the cycle are not present at the same instant, so while each point experiences the entire wave, only a specific point of the wave is present at any one instant, so the body "feels" each different point at the proper time, and the pathogens get shaken - as needed, to disrupt their activity.
For more details, please check the link: