Here's how buttons on earphones work (hint: voltage dividers)

I just learned how the buttons on wired headphones work. I've always wondered because the 3.5mm plug has just four terminals, and they're already occupied by the left and right channels, the microphone and the common ground connection.
To my surprise, it is not difficult to make multiple buttons work using just two pins -- the microphone and ground, in this case. (Does not apply to iPhones.)
The buttons, and there can be up to four of them, use a simple voltage divider network to send commands to the phone they're connected to.
Related Android article:
source.android...
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[@bearb1asting]

The cellular audio interference is amazing. I also wonder if this is why left and right audio apst always hace dofferent levels as well.

[@hapsti]

u should mention how the AC mic wave forms can be differentiated from the buttons using a coupling capacitor (or DC blocking capacitor)

[@danilodistefanis5990]

What if you press more than one at the same time?

[@bob_mosavo]

Awesome ‼
Thanks 👍

[@eraldylli]

Very nice. So, the phone has the mcu that decodes the voltages/signals, right? If there is an mcu involved, why not use regular io pins. I guess this method only uses one io pin, instead of several.

[@LeftyMaker]

I bet it's all integrated into the audio chip, if not into the snapdragon/mediatec/whatever SoC the phone has.

[@eraldylli]

@@LeftyMaker You must be right, it probably is a feature widely adopted decades ago. Great content, keep it up.

[@shibinpp165]

Usefull

[@abhiramgnair5329]

nice explanation

[@Mounixr]

I liked your content keep it up🎉

[@rahkemfleming6672]

Very cool vid!

[@yanipro3978]

Добре
Вече ми е ясно ❤