[rcfox]

When I worked on audio firmware for the BlackBerry, one of the external devices I had to support was called a "security plug", which just shorted the headset mic and headphones to ground. It always seemed kind of silly to me because there was still the handset mic on the phone that could be activated separately.

[extraduder_ire]

Did an external mic not stop the internal one from working? I assume the plug was a box-checking exercise more than anything.

[rcfox]

I think the default audio routing was setup to stop the internal mic, but if you used the mixer API, you could do weird, custom things.