current output from the resonant circuit 118 is rectified by the rectifying diode 130 to a half wave output before being transferred to the integrator circuit 120 the integrator circuit 120 provides a slow charge and discharge for the second capacitor 134 which preferably maintains the voltage difference across the capacitor at a threshold level for several seconds the integrator circuit provides hold time and automatic resetting for the lightning indication to remain active even if the external monitoring equipment 124 is itself upset by the event when the second capacitor 134 is at a threshold level measured by the gate threshold of the transistor 122 the circuit between the source 138 and drain 140 is closed allowing current to flow through the transistor from the external monitoring equipment 124 to ground the external monitoring equipment 124 is an external monitoring apparatus that may be installed in the aircraft and may be a standard aircraft equipment interface such as an open ground discrete which senses the electrical open ground discrete signal made by the circuit 116 and then uses this for fault or maintenance indication logic the zener diode 142 ensures that the voltage from the transistor gate to source does not reach a level that might damage the transistor 122 or other components the drain diode 144 is positioned between the external monitoring equipment 124 and transistor 122 and allows current to flow from the external monitoring equipment 124 through the transistor this arrangement ensures that current cannot flow from the transistor 122 to the external monitoring equipment 124 and cause damage in case of.