>>2768236http://home.howstuffworks.com/toaster4.htmI am. Toasters with the "one slice" requirement use a bi-metallic strip. Higher end models use a timer which is really a capacitor, which can be thought of like one of those bamboo noise makers. When it fills up, it tips over, releasing the toast. Obviously a capacitor is filling with voltage and doesn't really tip, but it's a good layman's analogy.
The darkness control in these instances is a variable resister, which can be thought of as a faucet handle. it lets you control how fast the bamboo cup/capacitor fills. In cheaper bi-metallic strip toasters, the lever physically increases the distance between the electromagnetic switch that holds down the toast so that it takes longer to bend far enough to trigger the release.
I tear apart way too many gadgets.