Chosen Solution
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?
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.
