What are internal switches? Answered
I've been searching out parts on digikey, and noticed that a lot of the power/audio jacks had an "internal switch", with three conductors and four contacts. I've never heard of these before, and none of the datasheets were helpful, nor ten minutes of googling, in educating me. So what are these mysterious internal switches? I presume they somehow switch between two states depending on if there's a plug in the jack. But why is this helpful or necessary? And more importantly, how does this affect how to wire the jack?