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My dad installed them throughout our house in the fifties and sixties. Didn’t understand how special they were til now.

I grew up in a house that was built in 1929 in California that had mercury switches. They worked perfectly when we sold the house in 2001. One side effect, though: In 1971, there was a 6.6 magnitude earthquake centered about 12 miles away. The shaking was so severe that the mercury connected and disconnected rapidly and randomly, causing all the lights in the house to flash in such a way for my mother to think that the house was on fire. That’s something you won’t see again in a house with modern switches.

I was expecting it to be illegal because of some obscure reason why switches have to make a sound, but this was just as interesting.

My grandpa had these in his house. When he and my grandma sold their home, I remember someone admiring the silent light switches and me being a kid I said "yeah, they're old, the sound is broken". He chuckled at me as I was too young to realize that they were designed to be perfectly quiet. Really cool to now learn that they were special and had mercury inside.

Mercury dangerous and poisonous? Give me a break. When I was a kid I remember finding these liquid metal in a glass shell and cracking them open to play with them with my bare hands. Nothing bad ever happened to me nor did I suffer any medical repercussions.

I remember as a kid in the '60s getting to hold a glob of mercury in 3rd grade science class. People had no idea of how dangerous that was.

I think switches are made today with a distinct click and they’re spring loaded so that they don’t get stuck in the middle, possibly causing an arc. These ones don’t seem to have that ability, theoretically it seems like you could have the switch just barely on or off and could be unsafe, especially with 120v, whereas the thermostats are 24v

Dad converted a van into a camper (back in the 70's) and put two of those in it for the overhead lights. When traveling, it had the side effect of occasionally flickering if we drove over some major bump in the road and the flash at night would be starling. Not sure why, but this memory brought back good vacation memories in that van!

When’s the last time you saw someone say “ hey your light switch is too loud” 😂😂

There was an old Atari joystick that used mercury switches too. It’s how they made motion-sensing joysticks before MEMS accelerometers. ;)

I remember replacing these mercury switches in the 1950's. The mercury inside the capsule would get dirty from the internal arcing, and a fine layer of powdery stuff would accumulate on the surface of the mercury. This powder inhibits a good contact, and the lights dim while heating up the switch. My dad used a hammer to open the capsules and show me the mercury covered with powder. Good thing the switch housings were made of ceramic, and that kept the house from burning down.

Years ago, my then-girlfriend (now wife) and her brothers "volunteered" me to drive across the country and remodel their mother's kitchen as a Christmas gift. They paid the materials and expenses, and I did the labor. Well, the house had been built in '56, and still had the original service entrance and wiring, which was now overloaded and a dangerous mess, so before I could start on the kitchen I had to rewire the house from the weather head down. One of the crazy things I found when doing this was exactly why they sometimes had no hot water. The water heater had been replaced sometime in the 90s by "the best plumbing company in town". They fed the heater (single element, 120v) with 12 gauge Romex, no conduit, no bonding, no insulated nipples and screwed a J-box to the floor joist over the heater and installed a switch there to act as a disconnect for the heater, The box was kinda horizontal with a single screw into the joist, and they used a mercury switch. If you stood in a certain part of the kitchen next to the countertop (where my father-in-law would stand to dry dishes as my mother-in-law washed them), the joist flexed and the switch would often shut off. There was a slew of other violations I corrected as I went along but that switch still makes me shake my head and wonder what they were thinking.

My grandparents' house has these noiseless switches. I'd awlays wondered how they worked. I'm gonna have to replace them before we sell the house because things like this fascinate me.

I was an instructor at one of the tech schools for the US Air Force. The base was located in Texas and one group of students were hot and wanted the AC to turn on. They decided the best way to do this would be to:

A major problem with these light switches is that if excessive current is passed through them, they vaporize the mercury and the enclosure explodes violently, spreading mercury all over the place.

Can we just take a moment to appreciate the length of this video? It's exactly right; there is a reasonably comprehensive history and explanation, physical demonstration, and good information throughout. At no point is it derailed for any nonsense filler or sponsor spots or anything, just very tightly packed information.

This reminded me of when a vacuum cleaner company, don't remember which one, made one that was absolutely quiet, but people wouldn't buy it because they believed that if it was quiet that meant that it wasn't actually cleaning. So they made the vacuum cleaner loud again.

I’ve definitely run into switches like this in some older buildings I’ve been in. In fact I remember being a kid very intrigued by the silent switches I’d run into, turning them on and off.

Back in the late 70s and 80s, mercury was used in ALL KINDS of things. They even made a light stick game controller for the Atari that had full motion controls by using mercury inside the stick to make connections on a 4 axis tilt that allowed you to control the game.