http://www.youtube.com/watch?v=OjxsQrrDGskThis is at the fixture near the door of the copying room of the storage of Carmel hospital.
Its continuously flickers 50hz because the thermal starter don't closes.
Flickering on the mains supply on modern magnetic ballast with either glow or electronic starter of fluorescent lamps, or in any type of discharge lamps, is as a result of rectification and in fluorescent lamps, as a result of weak starter or glow starter stuck in open.