Talk about taking for granted. In the first sentence of this article, I will use a switch about 100 times. Yet in the thousands of time I use contact switches as part of my job, I never terribly think about it.

This is a contact switch

A contact switch is any mechanical method for controlling whether or not electricity passes from point to point. The switch was invented in the 19th century as a more-or-less mandatory part of understanding how to experiment with electricity, and needless to say the very first switches that came into people’s homes were used to turn lights on and off. Later, switches were used to turn on appliances. Today, however, switches are so common that we don’t think about them.

What’s a non-contact switch?

There is such a thing as a non-contact switch. This is also a very common thing since there are millions of them in every computerized devices. A non-contact switch, or electronic switch or gate, is a switch where the flow of electricity is controlled purely by logic. Solid state switches are a key part of how computers work. Without them your typical phone would have to be the size of a fire engine to accommodate all the mechanical switches it would need.

How are contact switches used?

Turn your computer on, you’re using one switch or maybe two. There may be a rocker switch that actually controls the flow of power while a soft-touch switch signals a circuit that actually begins the startup process. Under every single key in your keyboard is a switch. The buttons in your mouse are switches too. The switch, it seems, is really the only way to communicate with a computer until you get it to the point where it can accept voice or gestural commands.

Phones are full of switches

Even the touch-sensitive surfaces of smartphones and tablets contain thousands of tiny switches that respond to the pressure of your touch. The contacts are so close that the gentlest touch causes them to flip on. Every button on your remote control, every controller, every knob, they’re all switches of some sort or other.

Seriously, try to make it an hour without pushing a button, flipping a switch or tapping a screen. You can’t do it, unless you’re sleeping or doing other recreational activities. Every bit of technology we have today is utterly dependent on switches.

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About the Author

Stuart Sweet
Stuart Sweet is the editor-in-chief of The Solid Signal Blog and a "master plumber" at Signal Group, LLC. He is the author of over 9,000 articles and longform tutorials including many posted here. Reach him by clicking on "Contact the Editor" at the bottom of this page.