Update: Just to clarify, this post is speculation, not fact. Based on the excellent iFixit teardowns it looks like the iPad 2 headphone jack has pins on both sides, which is more in line with Apple's typical cantilever design (roughly similar to the jack in the Macbook Air). Interestingly, it looks like the single-side pogo pin design may have made its way into the 4th generation iPod Shuffle. My iPad 2 is on order, and I have the appropriate amount of envy for those of you who have one right now.

Last September a few of the more ardent Apple blogs reported that Apple has applied for a patent for a smaller audio jack design using pogo pins instead of the more traditional switch contacts. The patent sketch looks like this:

It looks like the iPad 2 may be the first device to use the new pogo pin design. Interestingly, challenged to not only make the jack as thin as possible to fit in the iPad 2's form factor, it's also set in to a steep curve:

The original iPhone also placed the headphone jack on a curved exterior surface, but did so by insetting it, with the disastrous side-effect that only headphone plugs that strictly adhered to the spec would fit deep enough into the recessed space to complete the connection.

This time however it looks like there's no recession at all. In fact, the opposite seems to be true: A plug fully inserted into the jack will have a surprisingly large portion of its ground ring (the outermost metal band) exposed to the elements.

This probably won't be a problem, since the ground ring is, well, grounded, so touching it with something shouldn't produce much if any static, but it's an interesting design decision nonetheless. It's interesting to go to the iPad site and note how carefully Apple avoids showing the headphone jack in most of its video and photography, while highlighting every other design element of the device. You also never see any photos with anything plugged in to the jack.

One final thought on the new plug design is that it seems that these plugs could be waterproof. Unlike the common cantilever or switch contact designs, the pogo plug enables the jack to be completely sealed against the elements, limiting any fluid damage to the function of the pogo plugs themselves.