If you live in a nice neighborhood that has a sense of community, you may have come across a Little Free Library. Those are small cabinets filled with books that anyone can take. Ideally, people will also leave books for others. They’re usually situated next to sidewalks where passersby can stumble across them. Hackster.io currently has a contest challenging participants to build such a library dedicated to STEM and this inspired Amitabh Shrivastava to create a payphone that provides speakeasy-like access to his library.

Payphones are rare these days, so its mere existence should garner some attention. Anyone who looks at the payphone will then notice a message imploring them to dial 7836 for “STEM.” If they do so, the payphone will pop open to reveal the library inside. That is, of course, filled with books that can help people expand their knowledge on science, technology, engineering, and math. It adds a fun, interactive layer to the standard Little Free Library, while also demonstrating what a person can achieve with the knowledge within.

Shrivastava started this project with a real payphone that came from a laundromat. He then cracked that open to access the electronics inside and a score of $3.25 in loose change. Shrivastava added an Arduino Nano board to monitor the phone’s keypad and look for the numbers “7836.” If it sees those, it disengages a solenoid lock and the library door can swing open.

A custom cabinet ties the whole project together, providing plenty of space for books and conveying the desired aesthetic. This payphone will make its debut at Maker Faire Bay Area 2023 so you can see it for yourself if you’re heading to Mare Island this weekend or next, and will then inhabit the Avnet HQ building.