Abstract: A signal comparison and control unit including: a pre-processing module, pre-processing input signals to conform to processing requirements of a comparison module; the comparison module, comparing pre-set base signal parameters with output signal parameters from the pre-processing module and outputting a comparison result to a decision module; the decision module, with triggering conditions being preset, triggering output of electric signals or comparison data when the comparison result output by the signal comparison module matches the triggering conditions. Also an intrusion alarming unit and an invisible electronic fence constructed from the signal comparison and control unit. The signal comparison and control unit are capable of reducing false alarms.