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Inventor Tales - Square

Inventor Tales - Square

Sam Wen, named inventor of the Square card reader, tells some tales about the innovation process behind the world’s most famous POS device


Did you know that the Square card reader was almost called a “Squirrel”?!


In this first part of our ‘Inventor Tales’ series, we speak with Sam Wen who is the named inventor in the USPTO for the Square card reader.

The backstory to this interview with Sam is a serendipitous one! When we launched Retro Patents in January 2017, we were inundated with well wishers and supporters from around the world, it was awesome 🌎

But one particular share on Twitter stood out:


On first glance it took us some time to realise that the inventor of the patent that we had immortalised in print was sharing his own invention through the site. Then it was time for a celebratory high five 👋
So we reached out to Sam by mail and thanked him first and foremost for his support. It was a huge pat on the back from someone that we looked up to. It also made all the work that we’d put into getting Retro Patents off the ground worthwhile.
Sam even bought his own print from us which was the best validation we could get 👏

It’s easy to forget that a public company (SQ) all started with a simple product that was shaped by the hands of a few talented engineers and designers.

After a few exchanges back and forth, we asked Sam if he’d be willing to share some of the stories around the invention process for Square. We wanted to get the core of the innovation process itself and strip back the layers of abstraction.

So Sam kindly agreed to provide some more context about his role and highlight some of the challenges and takeaways from building the Square card reader. In his own words… 

Retro Patents: How did you get involved with Square in the first place?

Sam: I was working at a large defense contractor in Saint Louis and going to night classes, trying to get out of the defense industry. One of my professors offered to introduce me to a personal friend who was building an interesting startup. I listened in and found it to be a very cool idea with a very cool mission. I started working with Jim McKelvey the very next day.

What was the biggest challenge you faced with this particular invention?

Sam: The earliest readers were very simple devices; it was really just a simple LR circuit that directly send the raw, analog swipe signal into the microphone port. The problem is that microphones are often designed with band pass capabilities to filter noise. Unfortunately, depending on the speed of the swipe, we’d see every kind of filtering technique in the resulting signal read by our software. We had to work on this particular algorithm for quite some time before it would become ready to ship.

In addition, these were the days before iOS’s Accelerate framework, and some of the more advanced computational SDKs for Android, so any more advanced, frequency domain techniques for reading our signal was not possible. The entire algorithm in those days were done in the Time domain.

Any funny stories on the trials and tribulations (debugging it, launching it, setbacks etc)?

Sam: At the time, the tentative name was “Squirrel” (later changed when we realized that SquirrelPOS was already a company), and the Square reader was going to look like an Acorn. In fact, the original software written to support reading credit card data from the reader was called AcornKit.

Another funny story was that we made some initial prototypes out of aluminum. By then, we already had the algorithms, and were playing around with final industrial design. We couldn’t figure out why the aluminum prototypes performed so poorly, until we used an oscilloscope and realized the aluminum was conducting the electric potential in our fingers and acting like an EKG!

What are you most proud of with this invention?

Sam: Honestly, the fact that people use it and that it serves a concrete purpose. I get an immense feeling of satisfaction and responsibility when people use the Squares to power their business.

At Retro Patents, we celebrate innovation in tech, gaming and design 💡❤️

Massive thanks to Sam for his support and openness in chatting about the invention of the Square card reader.

If you want to check out the patent print itself, you can check it out here. If you enjoyed this post, we’d be really grateful if you could share it online, thank you 😄

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