A source of UV black light. These are self ballasted with a filament so doing away with the use of an external ballast. Uses are checking laundry marks paper money etc.
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https://www.youtube.com/watch?v=4rYcioptNUc
Interesting small neon indicators maybe for incorporating in switches etc to indicate when ON. These would require a high value resistor wired in series, note that famous trade mark the rounded M showing good quality.
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https://www.youtube.com/watch?v=m7Ujss5z-9I