The emitted electrons from small amounts of Tritium cause phosphors to glow so as to make self-illuminating devices called trasers which are now used in watches and exit signs. It is also used in certain countries to make glowing keychains. In recent years, the same process has been used to make self-illuminating gun sights for pistols and rifles. These take the place of Radium, which is chemically poisonous and so has been banned for decades.