October 2000
Intermediate to advanced
400 pages
13h 30m
English
Everybody knows that electricity makes things move. A brief glance around the average home reveals electric motors in appliances as diverse as clocks, fans, food processors, and compact disc players. Electricity also makes the cones in loudspeakers vibrate, bringing forth sounds, speech, and music from the stereo system and the television set. But perhaps the simplest and most elegant way that electricity makes things move is illustrated by a class of devices that are quickly disappearing as electronic counterparts replace them. I refer to the marvelously retro electric buzzers and bells.
Consider a relay wired this way with a switch and battery:
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