Tip-Ring-Ring-Sleeve style audio cables are often used for situations where you want stereo audio and then an extra contact for a microphone input. For example, headsets for cell phones. Also called TRRS jacks for short, they're also handy if you happen to want to use common audio cables for low-speed data transmission with power, ground and two data lines.This breakout board is simple but has everything you need to interface with TRRS cables: not only do you get the four contacts but also two switched...