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modern legacy: 3.5mm headphone jack

Although modern technology moves forward at breakneck speed, there are still old-fashioned solutions that are resilient enough to stand the test of time. Like digital equivalents of living fossils, they have managed to survive the disruptive effect of technological innovation and still thrive in highly modern IT-environments.

In this series, we will take a closer look at some of these technological dinosaurs that are still present in our modern times. This article will take a closer look at a familiar icon that everyone who regularly uses a wired pair of headphones will immediately recognize: the 3.5 millimeter headphone jack.

Your good old trusted audio partner

Listening to some relaxing music when you’re hard at work or cruising down the road in your beloved four-wheeled companion? Or chatting with your colleagues or friends without getting distracted by the drilling and hammering sounds of your busy and handyman neighbor? To provide us with these moments of joy and relief we have long looked at one close companion: the 3.5 mm headphone jack that we use to connect a pair of stereo headphones to our smartphone or computer. The headphone jack also allows you to ‘pipe’ audio from your phone to an external amp, either in your home or your car.

Nineteenth-century origins

The origins of the 3.5 mm headphone jack go back a long way. Believe it or not, our beloved and familiar industry-standard audio plug is actually a nineteenth-century piece of technological kit. It’s basically a miniaturized version of the classic quarter-inch jack (6.35mm), which is said to go back as far as 1878. This classic piece of equipment was used by operators in old-fashioned telephone switchboards to plug and unplug connections.

When miniaturization set in (an ongoing trend that nowadays sometimes reaches almost ridiculous proportions) and audio equipment changed, the quarter-inch jack needed a smaller, more compact successor. The 3.5 mm headphone jack quickly captured the heart of the tech community and regular consumer, particularly because people became incredibly fond of personal headsets for transistor radios.

Solid and trusted design

Although audio and headphone technology have evolved over time, the basic design of the 3.5 mm headphone jack has changed little. The jack consists of a tip, ring and sleeve (TRS connection). The tip transfers audio into the left-hand earplug of a stereo headphone set, whilst the ring does the same on the right. The sleeve is the ground or “shield” that adds stability to the design.

Assassination attempts

During its long and impressive lifespan, the 3.5 mm headphone jack has faced several assassination attempts by more modern tech rivals. OMTP and CTIA used roughly the same principles, with the difference that the ground and microphone connection were swapped around. Those extra connections were also used for volume up and down buttons on inline remotes. However, you had to buy a headset compatible with your phone if you wanted the mic and volume buttons to work. This made these technologies a lot less practical than the classical 3.5 mm headphone jack.

USB technology also took some serious swings at killing off the 3.5 mm jack, most noticeably with the introduction of the USB Type-C connector. Despite being hit by several waves of technological innovation, the 3.5 mm headphone jack still stands strong in the eye of the impetuous storm of digital disruption. The main reason for its longevity? The simple fact that devices with a 3.5 mm headphone jack are compatible with just about every pair of headphones made in the last seventy years…