Lightning Protection for Status and Control Lines of the Mark III Instrument Landing System

The lightning protection requirements for solid state circuits of the Mark III ILS which are connected to buried control cables are presented. Susceptible circuits consist of transistor switches, relays, and dc power supplies. Avalanche diode surge protectors with associated resistance are used to protect the circuits from the worst-case 1000-volt, 10 × 1000 μsec surge waveform expected.