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Hi, just wondering why does the iphone 5s and other iPhones upwards have 4 pins on the ear speaker?
I know the 2 outer pins power the speaker but what are the 2 inner pins for?
Is this a good question?
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This is a great question and made me learn something new today. I've often wondered about those four pins as well but never really gave it much thought.
Looking at the schematic, I noticed that the section for the ear speaker has four lines, two for the receiver and two for CODEC_TO_HAC. Now I haven't checked this via continuity testing of the flex but everything else on that page refers to the FCAM and sensors so this makes sense.
A quick search highlights that HAC probably refers to "Hearing Aid Compatible" and this Apple support page explains how the ear speaker adapts to hearing aides.
So there you have it...unless someone else has explored this and found something different.
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If you read through this question and answer and don't feel like it was a waste of time...you might be a nerd. Thanks Minho
My pleasure Sean!
Thank you Minho, i repair iPhones everyday and every other part of the phone makes sense and shows up on a google search if needed but this one didn't!
The other two terminals connect to the inductive loop transmitter. Inductive loop is a very simple loop of wire usually (just one turn) that is able to inductively transmit the audio to a tele-coil equipped hearing aid. The tele-coil looks very similar to a tiny version of an AM antenna. A tiny solenoid wound on a ferromagnetic core.
Inductive loop audio transmission is a widely used wireless transmission technology in hearing aids. Apple makes it a little mysterious by calling it an "HAC radiator".
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