We are always surprised that Amazon or Google doesn’t employ Kelsey Grammer — TV’s Frasier — as a spokesman for their smart home devices. After all, his catchphrase was, “I’m listening…” Maybe they don’t want to remind you that the device could, theoretically, be sending everything you say to them or a nefarious hacker or government agency. Sure, there’s a mute button and it lights up a red LED.
But if you are truly paranoid, that’s not enough. After all, the same people want to eavesdrop on you would be happy to fake a red light. [Electronupdate] had the same thought and decided to answer the question: does the mute button really mute your microphone? The answer required not only some case opening and analysis, but there was even some IC decapsulation.
We were impressed with the depth of the analysis. The tiny SMD parts are marked confusingly, and if you are really paranoid you don’t believe them anyway. But looking at the actual circuit die is pretty unambiguous. The parts in question turned out to be a Schmitt trigger, a flip flop, and a NAND gate.
In the end, it appears that the red mute light comes on when the microphone has no power. So it looks like the mute button is real. The comments are already speculating ways that a spy could listen in even with the red light on — or at least appearing on, but it isn’t clear that would really be possible.