There is a similar plug in the cockpit of many airliners 320s 300s and 727s from personal experience. Many times I have plugged my laptop or my cellphone charger into those plugs with no bad effects.. .. .In all cases the powersupply converts the power to DC which doesn't have cycles so it shouldn't care whether it is 60 hz 400hz or 4 million hz.... .. .You wouldn't want to plug an your hairdrier in however has it would run at 8 times the normal speed..... .. .Cheers. .Wino