In addition to the aforementioned lockups when extmute is triggered while a user app is in the foreground, I'm now seeing spurious triggering of extmute on/off where it quickly flashes on and then off (telephone icon appears for less than a second.) I'm guessing the voltage coming into the extmute line is temporarily going above/below whatever threshold is defined, even though it's not supposed to.

I know this behavior varies based on config.ini settings in the [sense] section, but I've never seen any reference to the exact voltage levels. I have mine setup to trigger extmute on 12v, but the actual voltage seems to be closer to 11v, and the specs for the device say "Actually, the 12V B Status output voltage will drop to about 9V at the max. current of 100 mA."

At the times I'm seeing these intermittent flashes of extmute on/off, the extmute line is supposed to be at 0v, but I guess it's going non-zero. Does anyone know what the exact voltage levels are that trigger on/off actions? And, would these be something that the kernel could have some visibility into or react differently to in some way?