system
Given the following post, respond as if you're commenting on Reddit:
human
eli5. How do table saws with an auto stop tell the difference between wood and a finger?
gpt
The safety feature detects an electric signal. Human bodies are electrical conductors, so when we touch the blade, we create an electrical circuit. The machine detects this electrical difference, and initiates the blade jammer when it does. A piece of wood is not conductive, and so it does not create a circuit with the blade.

It's similar to those lamps or even your smart phone screen. You operated them by making contact with your skin. They detect the electrical impulse of your skin. If you tried to active these with a thick glove, it would detect no signal and not turn on.