incomplete current path through a buzzer 31 the 34 1 34 level on conductor 24a is inverted twice by inverters 25 and 26 to transfer a 34 1 34 on one terminal of resistor 29 causing current to flow and illuminate three anodes 30b 30c and 30d which are connected to the other terminal of resistor 29 at the same time current flows through the other three anodes 30a 30f and 30e and illuminate these anodes in this way the seven segment led 30 reads 34 0 34 and no audio signal sounds when inserting a packaged esd sensor 10 into socket 54 the state of conductor 24a depends on the resistance of the gate oxide 46 of mosfet 11 if the gate oxide remains intact unruptured after exposure to an esd event the high resistance of the gate oxide maintains a 34 1 34 state on a conductor 24a if the gate oxide 46 of mosfet 11 is stressed by an esd event the state of the conductor 24a is switched to a 34 0 34 level due to the low resistance of the stressed or ruptured gate oxide on the same basis of circuit operation the second and third inverters 26 and 27 produce a 34 0 34 and a 34 1 34 at each output terminal respectively the combination of a 34 1 34 level on one terminal of resistor 28a and a 34 0 34.