Penthouse Light/Wiring Loom in Lubrication, Batteries & Electrics Posted August 2 I would think that the purpose of the earthed shielding is two fold. 1. To minimise the radiation of the oscillator and its harmonics that drives the inverter supplementing the RF filtering within the lighting units. So minimising RFI to nearby comms equipment & I suppose reduce a permanent RF signature to an enemy who might be able to detect activity in an otherwise closed down situation in the battlefield. 2. To minimise the pick up stray RF fields or EMP that may be present in the vicinity & cause voltage fluctuations or damage to the lighting units.