The AN90 clips directly on to fence wire. It has an on/off switch for easy relocation and battery saving. It has two pulse speeds. You can choose slow mode for improved battery conservation. It can be powered internally with 4 D batteries or externally with a 6, 9 or 12 V battery, or add a solar panel for increased battery life. Switching between the options is simple. When using a solar panel the battery power kicks in only when sunlight conditions are insufficient. A flashing LED provides a quick visual indication of the fence pulse. When operating on fences with low loads the energizer automatically uses excess stored energy to recharge itself for the next pulse which extends battery life.