Have you ever heard a dial tone or a busy signal? How did we call someone before speed dial and push-button telephones, but after people stopped needing to speak with a switchboard operator? Behold the rotary dial:

“…a component of a telephone or a telephone switchboard that implements a signaling technology in telecommunications known as pulse dialing. It is used when initiating a telephone call to transmit the destination telephone number to a telephone exchange.

On the rotary dial, the digits are arranged in a circular layout so that a finger wheel may be rotated with one finger from the position of each digit to a fixed stop position, implemented by the finger stop, which is a mechanical barrier to prevent further rotation.”

It was first patented in 1892 and became popular around 1919. The Introduction to the Dial Telephone short 1936 newsreel above, courtesy of the AT&T Archives and History Center, was shown in movie theaters before the movie to help people learn how to dial, how to recognize dial tone, and how to recognize a busy signal.

It took decades for dial to sweep the entire Bell System. The last holdout was Catalina Island, off the coast of California, which finally converted to dial in 1978. In Camp Shohola, Pennsylvania, an internal automatic switch system still connects campers with the outside world, it’s the oldest functioning Strowger switch in the world.

Here’s a 1954 PSA-style explainer from the AT&T Archives that includes background on how cables were installed and transitioned from the previous technology. Demonstrator Susann Shaw explains slowly and in great detail: Now You Can Dial!

Next, watch Morse Code, The Museum of Obsolete Objects, 40 Years of Cellphone, and The Story of Light – Future Impossible by Bell Labs.

Plus: Thin underwater cables hold the internet, The Story of Send, and The Master Microfixer Teaching the World to Fix iPhones.

h/t Kottke.

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