I actually owned one of the little iPod Shuffles and was struck at the time by the cleverness of using the headphone jack as a charging port using this little adapter.
The principle at work
All previous devices of this ilk would use one jack for charging and another for the headphones. So what Principle is at work here? Is it Principle 5 – Merging, wherein two things are made into one? Or is it Principle 6 – Universality, wherein one thing is given a second purpose?
I am leaning to Universality. Merging is when you take two things like a clock and a radio and make it into a third thing, a hybrid of the two. In this case the headphone jack is still a headphone jack. Only the internal circuitry is changed. This takes a headphone jack and gives it a second purpose.
Am I overthinking this? I talk at some length about how much distinguishing between the 40 Principles matters in another post.