not bulbs acorn,they are a electronic device that allows current in only one direction,they are arsenic infused
so that they glow when a current flows through then,
if you add a gate trigger it becomes a triac that allows more current to flow through the more you apply power at the gate,its used in light dimmers,and speed control devices,i used to fit them in the neutral return in car radios and cb units,incase the user reverses the polarity,so it wont damage the unit,but i used ordinary diodes.
gts
April 2011