I have been trying to create a HD audio dongle that does not, as is normally the case, automatically detect the insertion of an audio cable when it is plugged in, but rather allows the user to control the detection via a physical button, which is notably also supposed to feature an LED indicator light so as to show when the jack is active.
According to the HD audio specification, typically an isolated, normally open switch is used for this inside the jack.
Now I am not sure what exactly would be necessary to emulate the behavior of such a switch. Since my button features an indicator LED it draws some current and would consequently mess with the Motherboard's detection circuitry, which relies on precise resistances. Therefore I would have to somehow switch separately, which could be achieved using a MOSFET. However this solution would not technically be isolated and I do not know if this could be troublesome. I am also not sure if a P- or N-channel MOSFET would be correct for this application, because the exact way that the jack detection network works is not specified.
My current working hypothesis is that a P-channel MOSFET is the correct solution, but I would like to confirm this.