Abstract: A security fence system employs a plurality of very thin, high tensile strength, highly stressed wires arranged relatively close together and between each of which is connected an electrical resistance. A voltage source causes a current to flow through the series-connected wires and resistors. An annealed segment can be formed in each high tensile strength wire and located between the points where each wire is attached to the fence posts, to make stretching of the wires without breaking them impossible. A sensing circuit is connected to the fence and includes voltage comparators and potentiometers for providing adjustable triggering levels. The comparators detect when the current flowing in the fence is altered and trigger an alarm if any of the wires are broken, or if any of the wires contact one another. The alarm can be turned off only by normalizing the fence and actuating a reset switch.