When I plug in a pair of headphones in the back of my tv, it cuts of the sound to the speakers. But If a I plug just an unsoldered 3.5mm jack, it still cuts of the sound to the speakers. How does it know there is a jack plugged in when, technically, the circuitry would detect that as the same as nothing in there. It's really just extending the leads by a little bit, with no connections being made. Is there an extra sensor in there the gets shorted when a jack goes in?