What is the push button at the top of a Wave unit?

Each Wave unnit comes with a Current Assurance button. When the unit is on, if you press the button the light above the LEDs with flash at the frequency of the Wave and will change colors if that wave also reverses polarity. The same current delivered to the client is used to light the light. Co, if the Current Assurance light is illuminated, current is being delivered to the client whether they feel it or not.

The switch in momentary, meaning testing is happening only when the button is held in the down position.