October 15, 2005 9:53 PM Subscribe
How does a stoplight know what time it is?
posted by hobbes103 to Technology (14 answers total)
Around my house, after midnight, a bunch of stoplights will start to blink yellow, instead of operating normally. Another example are lights at certain intersections that have different timings at different times during the day. Obviously, these stoplights have a clock of some sort, but how is it set? Do they receive a signal of some type, maybe from the power lines? Or are they set once and then forgotten? If so, how do stoplights deal with daylight savings?