Fuse carriers with fuse fail neons

I suspect it is maybe a regs fail, but not actually a problem in practice, and very common in certain types of field kit designed to use "power of opportunity" in which ever country the kit ends up being dropped into.

Although disapproved of, there are such things as neon screwdrivers, where the current to light the lamp flows through the body of the user - the point is it is quite possible to light the smaller sizes of neon indicator without exposing any downstream worker to a dangerous voltage or even a current large enough to cause a sensation they would be able to detect. They do  need a minimum current of a hundred microamps or so to operate, and indeed some load is needed to ensures the collapse of the load -side voltage to a safe value. Even with all loads off, unless the circuit is very short, the wiring capacitance will pass enough to keep the neon on.- a thousand pF (10 metres) is of order 3j megohms at 50Hz, and is enough to strike a dim light. If this  is an  issue then an RC snubber at the exit terminals can be used to provide a minimum load.

I have certainly designed fixed kit with this feature in, but you won't be able to get a true open circuit in meggar terms with the fuse out and to be pukka  it probably needs an additional all-pole isolator, and a warning to use it before opening the box.

I suspect it is maybe a regs fail, but not actually a problem in practice, and very common in certain types of field kit designed to use "power of opportunity" in which ever country the kit ends up being dropped into.

Although disapproved of, there are such things as neon screwdrivers, where the current to light the lamp flows through the body of the user - the point is it is quite possible to light the smaller sizes of neon indicator without exposing any downstream worker to a dangerous voltage or even a current large enough to cause a sensation they would be able to detect. They do  need a minimum current of a hundred microamps or so to operate, and indeed some load is needed to ensures the collapse of the load -side voltage to a safe value. Even with all loads off, unless the circuit is very short, the wiring capacitance will pass enough to keep the neon on.- a thousand pF (10 metres) is of order 3j megohms at 50Hz, and is enough to strike a dim light. If this  is an  issue then an RC snubber at the exit terminals can be used to provide a minimum load.

I have certainly designed fixed kit with this feature in, but you won't be able to get a true open circuit in meggar terms with the fuse out and to be pukka  it probably needs an additional all-pole isolator, and a warning to use it before opening the box.