The Electric Fence Light is designed to let you know that your electric fence is working properly without any worries. It flashes on and off with every pulse of the fencer with very little draw down of the voltage. Due to the line current, this light is ideal for fencers under 3 joules. The Electric Fence Lights only draw current from your fence until the moment something touches the fence. If something touches the fence, the light will not flash and the full charge will go to whatever is touching your fence. So don’t worry if your tester is showing a draw down on your fence while the light is flashing. Note: Adjust the Knocker spark gap as wide as you can with it still being able to spark. This sensitizes the spark gap with your entire fence, and if something touches the fence, the Knocker spark gap will disengage and the full shock of the charger will go to whatever is touching your fence.