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All this crankiness about the iPhone's new, smaller dock connector—the thin, rectangular port at the bottom that your phone charger plugs into—has made us appreciate the stability of the phone's other port: The TRRS connector, or in regular-people speak, the headphone jack. That, too, has changed with this latest iteration of the phone, now appearing on the bottom rather than the top (pictured above) of the iPhone. But that relocation won't require a $30 adapter, or a whole line of new accessories -- the actual hole hasn't evolved. In fact, unlike the 30-pin dock connector, which Apple introduced in 2003 with the third generation iPod and 9 years later has opted to change to 18 pins, the TRS port hasn't changed since its invention in the late 1800s.  It comes in various sizes, with the iPhone and other smartphones sticking with 3.5 mms. Smartphones use TRRS rather than TRS connectors because they have an extra ring for microphone capabilities. But, across all of our devices, Apple or not, we can count on that orifice, the jack, staying constant. Here's to that.

When we say the cable hasn't changed much since its invention, we mean in both form and function. The first evidence we can find of the cord is this patent filing for a "plug and spring jack for telephone boards" from 1895 (pictured right) that seems to correspond with the modern TRS. "The invention is applied particularly to a 'triple plug' and a corresponding 'three part spring jack,'" explains the patent, leading us to believe this is the same invention. The TRS name stands for the three rings, which make up a triple plug. Also, this Electrical Review article from 1903 says these triple plugs were used for telephone jacks during that time. The evidence adds up. 

As you can see, that patent drawing looks a lot like what we see today -- it almost looks like a hip throwback advertisement for an auxiliary cable. The final conception back then, which we see pictured below via International library of technology, didn't differ much in figure from either the older patent drawing, or the modern plugs we see today. For over 100 years, this plug has looked a lot like that. 

Though these originated in the telephone world, today we use them for all sorts of audio transmission, like headphones. But, even so, the basic use is the same as it was 100 years ago: To move sound. 

There was a moment when Apple tried to evolve it, in a way, giving the iPhone 2G a recessed headphone jack, which didn't jibe with non-Apple headphones, as ZDNet's Jason D O'Grady complained. Apple claimed it made the move to benefit phone owners, a source told O'Grady after his rant. "Apple found, prior to the iPhone, that a lot of service repairs for iPods were for busted headphone jacks caused by headphone plugs being constrained, pulled, or bent in pockets or other tight areas. This is why they recessed the iPhone's headphone jack into the casing," this anonymous person said. But that move didn't inspire a line of new accessories to fit the Apple standard. People begrudgingly got adapters until Apple went back to the old way of doing things for the iPhone 3G, thus appeasing the critics. "That recessed jack was one of the most ridiculous design decisions in the original iPhone, and it’s great to see that Apple has addressed the problem and made the iPhone 3G accessible to just about any set of headphones in existence," wrote MacWorld's Jason Snell in his review. Since, the iPhone has had that same hole. 

The smartest of iPhone accessory makers have taken advantage of this stability -- when they can. The technological capability of the dock-connector differs from that of a jack, so it's not always possible to bypass the dock-connector altogether, as Cult of Mac's John Brownlee points out. "It allows an iPhone, an iPad or an iPod to talk directly to compatible accessories, no drivers required. It’s the soul of Apple’s billion-dollar iPod, iPhone and iPad accessory empire. And it’s secretly one of the best inventions Apple’s ever made," he writes, explaining that USB ports or the jack can't do those things. The iPod Shuffle managed to bypass the need for this connector (pictured right, via Apple), however, using the jack to both charge and move USB data in and out of the music player. All other Apple devices, however, use the dock-connector because it makes add-ons possible. (There are a "negligible number of third-party accessories" for the Shuffle, notes Brownlee.) 

But companies like mobile payments service Square and Incipio, which makes all sorts of iPhone accessories, didn't put all of their faith in the now obsolete 30-pin port, looking to the sturdy headphone jack instead. To be fair, some accessory makers have an easier time using the headphone jack. This microphone attachment from Incipio, for example, just had to tap into the natural technological capabilities of a TRRS port. With Square, however, the doo-dad (pictured left) scans the magnetic strip and converts the data to an audio signal all set for that headphone jack to accept. That's extra genius, now that the company doesn't have to think about converters for all the small businesses that have adopted its device. 

The jack can't do everything -- it won't act as a direct charging port, for example -- so, we understand why some accessories makers, like all those clock radio manufacturers that have now forced hotel owners to pay up for $30 adapters, went with the 30-pin connector. But we appreciate the consistency of that traditional port as well as the accessory makers who went for utilizing its simplicity over the pronged attachment. 

This article is from the archive of our partner The Wire.

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