This fence tester lights up if your electric fence is not functioning correctly. No more wondering if your electric fence is working. The Fence Alert clips on to fence wire or tape and has a flashing light that indicates when the fence has low or intermittent voltage. The Fence Alert only lights up when your fence voltage drops below a set point; the cut-off point is adjustable with a simple switch on the back of the unit. The Fence Alert will NOT flash if your fence is working properly. No more walking fences at night as the light can be seen up to one mile. It will fit on wire as big as 8 gauge and polytape up to 1.5". Please note that this model is designed for use with energizers that produce a pulsed charge, and is not recommended for use with solid-state or continuous-charge energizers.