Abstract: The security device receives longitudinal tension from a taut wire of a fence and preferably is placed in-line in the taut wire system away from posts used to support the fence. The security device senses variations in the longitudinal tension in the taut wire and produces a tension signal which is transmitted to a central location when it senses such a tension deviation. The security device may be used in conjunction with a resistance sensing device to provide further protection. The resistance of a conductive loop formed either by the taut wire or by the combination of the taut wire and another conductor is monitored and a resistance signal is produced when it senses either a discontinuity or a variation in the resistance of the loop. The method of the present invention includes steps for receiving the tension in the taut wire and producing a signal when the tension in the taut wire varies more than a triggering amount.