I've been testing a design on our system lately. The physical test is to plug a microphone into one jack, speakers into another jack, and when you speak into microphone, you should hear your voice over the speakers (sparing the technical details).

Last week, I ran a couple test vectors on the design, and it looked like the results were correct. And then I did the physical test, plugging in my headset which has both mic and earphones. From that, I could only get noise out of the earphones. After some back and forth with the team in the US, and no obvious solution.

Today, with the US team here for meetings, we tried it again... same result. And then after some quick investigation, the problem was found. My microphone has a little volume and on/off switch. Umm... it was off. DAMN IT.