alt Hacker NewsWouldn't you need to rewire the headphones? Headphones use a 3-pin TRS whereas a 4-pin TRRS plug is used when you add a microphone. Regardless if the 4-pin is CTIA or OMTP, it's generally only going to get shorted to ground if a 3-pin TRS plug is plugged into a 4-pin TRRS socket, or if a 4-pin TRRS plug is plugged into a 3-pin TRS socket.
Diagram: https://i.sstatic.net/8rSD2.jpg
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"Wouldn't you need to rewire the headphones?"
This is basic physics controlling the effect here, not electrical routing. Speakers are microphones by their very design. To make them work as a microphone, you merely speak into them with them plugged into an input jack that provides at minimum a line level electrical signal to be modified by wiggling the speaker cone/diaphragm back and forth.
Non-phone non-Apple devices often have a TRS microphone input separate from the TRS headphone output.