Thursday, December 9

Square played it to Apple with the minijack, and that story inevitably reminds us of the mythical Spectrum 48K

Square became famous for turning any iPhone or iPad into a POS that you could pay with. Simply connect a small accessory to the headphone port and voila!You already had a card reader that merchants used to process those payments.

The most curious thing about this accessory is that in Square they managed to play it with Apple, which theoretically only offered its Lightning connector. If you wanted to use it, you had to pay royalties and be blessed by the Cupertino company, but Square thought there was still another way to achieve their goal. Maybe they were inspired the beeps from modems and old Spectrum 48K.

Wait, we don’t need the Lightning port, there is a minijack

The story of how Square created its card reader is unique. It was told by Jim McKelvey, co-founder of Square with Jack Dorsey, who long ago published his book ‘The innovation stack’ to narrate precisely how they created and managed to bring Square to what it is today.

In that book there is a passage which precisely indicates that connecting a card reader to the iPhone “was risky.” The only way approved by Apple to do this was to use its data connector, the Lightning port, but “Apple had a long and expensive approval process“to use that connector, in addition to requiring”special chips you had to use, royalties on each unit, and a bunch of extra rules“apart from those already imposed by financial institutions.

However, Square engineers realized something: the iPhone, like almost any other mobile of the time, had a headphone jack, a minijack, which was oriented to receive audio signals.

It is at that moment that the light bulb went on: “if we could make the credit card data appear like the output of a microphone, we could read that magnetic stripe [de las tarjetas de crédito]”via the headphone jack.

It turns out that the SDK that Apple offered to developers described how to use audio the way Square intended, so the company was able to “write some code without having to ask anyone from Apple for permission.” By using the microphone jack to circumvent Apple’s dock connector standards, we were able to have a working prototype in a week“.

The Spectrum 48K taught us that the minijack was much more than it seemed

Some say that when Apple announced its controversial decision from remove the headphone port of the iPhone 7 He did it in part as revenge for what Square had accomplished, but that seems highly unlikely.


What is certain is that that decision – with all the controversy of ‘courage’ included– made Square have to search other ways to offer your services, which are now also based on point of sale terminals in the form of mobiles and tablets (although they keep selling readers that connect both to the headphone port and through the Lightning port).

The truth is that the idea of ​​using the headphone port to transmit data was by no means new. It was precisely what for example the old ZX Spectrum 48k did to save or load programs and data: the cassette player was connected via a minijack.

There are in fact who has finished managing for analyze audio files and then convert them into code that the ZX Spectrum 48k can understand.


Square has much more complete points of sale, but it continues to sell its readers with a minijack or Lightning port connection.

Projects that allow transfer data between two Android phones with an audio cable with a minijack at each end show that that’s another curious alternative to perform that process.

In fact, projects in this sense are so curious – as this web-based modem– What numerous, and in many cases takes advantage the concept that they also took advantage of the modems that were used to connect us to BBSs and the internet in the early days.

That, of course, had clear limits in terms of transmission speed, that through the telephone line could reach 8 kBps according Some studies. Very far from the 600 MB or more that today we usually achieve with fiber optic lines.