Know Your Fence is Working! For instant reassurance that your fence is working. Place permanently on your fence line and simply look for the flash (flashes with each pulse of the Energizer) when you pass by. No batteries required. To setup, clip onto the fence wire and push the lead into the ground. If the voltage drops below 3000V, the Live Fence Indicator starts to flash intermittently and if the voltage drops below 2000V, the Live Fence Indicator will stop flashing altogether.