And here's a page which explains some of the "ionization technology" used in smoke detectors, including in the $4.89 Walmart version of the one I have here:

http://www.angelfire.com/electronic/cwillis/rad/smoke.html

Wikipedia: http://en.wikipedia.org/wiki/Smoke_detector#Ionization

W says "A self-test circuit simulates an imbalance in the ionization chamber and verifies the function of power supply, electronics, and alarm device." .. but doesn't elaborate on how it "simulates an imbalance."


Edited by mlord (09/10/2013 20:16)