I have purchased several of these and have had good results. I just flipped the switch to the correct spot and clamped it on the fence when it was off. It immediatley started to blink indicating the fence is off. When I turned the fence back on it stopped blinking. Works great since I can see the blinking leaving and coming home early and late in the day.
"Does not work!"
Initially it appeared that the contact plate in the clip was positioned poorly and did not make good contact. It seemed that if you lifted it just right with your finger while it was clipped to the fence it would on occasion work for a pulse or two. After spending several hours trying to ensure better contact was made (experimented on all five devices), with no change in results, I took a meter to it. With a good voltage on the input wire there was absolutely no indication of device activity. Shut the voltage of, still no indication of device activity. It appears that what ever state it is in when the fence shuts off is the state it stays in. If it was blinking because you turned it on before you attached it to the fence, it keeps blinking when the fence shuts off. If you managed to get it to stop blinking while on a hot fence, then it does not blink when you shut the fence off. A great idea. I wished it worked. I would be interested in hearing from anyone who has gotten one of these to work.