@Caroline, What's that?
Not too known, Andy (photonicinduction) showcased one working, it's a type of incandescent lamp comprised of ballast (resistive element), a zirconium oxide rod
(glower) and a heater, the heater has lower resistance so it comes on before, heats up the glower and once it's hot enough it'll begin to conduct electricity in a stable manner, when that happens a relay activates and turns off the heater.
https://www.youtube.com/watch?v=-spTvp5-sf0