Whether hung on the wires or affixed to the posts, Electric Fence Current Monitors provide an instant visual indication of a power problem and where it is via the devices' flashing LED light, which is reportedly visible up to a mile. Speedrite monitors flash only when the fence's voltage drops below a pre-set level or there's a break. Gallagher monitors flash continually with each pulse of the fence's energizer, intermittently when voltage drops below 3,000 volts, and stop flashing altogether below 2,000 volts. Insulights will flash continually until a break occurs. (The latter two monitors' continual blinking also reportedly helps prevent deer and other animals from running through the fence.)