Bell Labs Could Send Sign Language Over The Phone - In 1979

Back in the good ‘ole days before the internet and Yo and Meerkat and Snapchat, we had one way to talk to people in faraway lands: the telephone. But a microphone and speaker aren’t much use if you’re hearing impaired.

In 1979, a Bell Labs research project devised a way of communicating with sign language, using just the bandwidth of one phone line. 35 years ago, video chat wasn’t feasible for most users, so the challenge was to distil sign language down to something that could be encoded and sent over the (very limited) bandwidth provided by a single phone line.

The solution was to place 27 retro-reflective dots on the hands and face of each individual, and then point a bright light and a camera at the signer. The dots — and only the dots — were detected by the transmitting device, which could then send the positional information to a screen at the other end. The researchers, Kenneth Knowlton and Vivien Tartter, outlined their achievement in this paper in Nature.


As well as being an impressive technological feat — remember, they pulled this off before the Walkman was a thing — it’s also a good lesson in designing technology around the user. It would have been easier to just force the hard-of-hearing to only use written communication, or learn some other, more machine-friendly sign language. But instead, Knowlton and Tartter found a solution with zero learning curve and total user-friendliness. Better than I can say for certain things today. [AT&T]

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“45 years ago” I think you meant 35 years ago. But regardless, this tech looked pretty cool!

One of my favorite parts of this video was Vivian Tartter explaining that they couldn’t use the whole picture to show the sign language because it would take the equivalent of “100 telephone lines to transmit.” I’m sure that seemed like a lot of bandwidth back in 1979, but would barely qualify as a decent RealPlayer stream circa 2000 in modern terms.

Here’s another of my favorites from the AT&T archives:

It’s a history of the US ballistic missile defense system up to 1976. Some of the technologies they developed were amazingly advanced, like the Sprint missile, capable of going from 0 to Mach 10 in only 5 seconds. Absolutely bonkers stuff. A long video, but worth the watch.