In the 1930s, Bill Gallagher developed a system of containment of his livestock on his small farm. His horse Joe was scratching on his car constantly; this sparked the idea for the first electric fence. It consisted of batteries and Ford car coils and led to the founding of the Gallagher Group, producers of electric fencing products.
Both the low and high impedance electric fences include an energizer or charger, high tensile wire, a ground rod and insulators. The ground rod attaches to the charger, which uses a jumper wire to attach to the wire and provide a shock to anything that touches it. The plastic insulators attach on wooden posts by nails or metal T-posts by wire, and the high tensile wire that carries the charge strings through them to enclose your area. An electric fence is safer than barbwire in that the livestock does not get injured on the wire.
A low impedance fence charger is useful for smaller animals like goats and sheep that do not push constantly on the fence. This type is also effective for smaller areas that lose less voltage over the course of the fence. Low impedance chargers are also functional for fence lines that do not have excessive weeds, trees and grass growing along them. A low impedance system does not have a weed burner and any grass or fallen limbs that touch the wire with ground it. Therefore, it will not cause a shock when touched and is ineffective in its control.
High impedance systems are valuable tools for larger stock as cows, swine and horses that like to push on the wire to get the grass on the other side of the fence. It is also helpful for longer fence lines to continue to be effective with some voltage loss over a long distance. High impedance systems also include a weed burner, which can effectively burn weeds and tall grass off the wire when they touch it. This type of electric controller can also burn through small tree limbs so that they do not ground your charge.
When installing an electric fence keep in mind the linear distance of your fence line and what type of animals you are containing. A ground rod works best in the lowest area of the property so that is stays moister and conducts more electricity. A high impedance fence charger will enable you to spend less time checking the lines for inconsistencies in charge due to the weed burner included.