Trying to answer iwire’s question “How does this cheaply made device 'know' how long 1 second is?” I want to say something previous to inventing of timer ICs (like the 555 you are talking about) more electrical than electronics (maybe not all the electricians in this forum know about flip-flops and comparators, but I’m sure they are more familiarized with resistors and capacitors):
The “time constant” of an R-C circuit (resistor and capacitor) is the time, in seconds, needed to charge that capacitor through that resistor at a value approximately equal to the 63% of the voltage applied to the circuit. So, for a circuit “to know” how long is 1 second (or any time period) is just a mater of doing the proper calculations at design time; no magic on it. Charging and discharging the capacitor is the way of doing an electrical pendulum (asymmetrical, by the way).
There is a nice little article that may help at http://www.tpub.com/neets/book2/3d.htm; it even has some graphs.
Joe.-
