DrAzzy:
and insert detect (connected to outside of the connector when a connector is plugged in - or when a connector isn't plugged in - one of the two. I'm not sure whether there's a standard on this).
For a power jack, this is not "insert detect", it is battery, and that is the standard. It was always used to disconnect the battery in a radio or similar appliance when a mains power supply is plugged in. The reason some rogue manufacturers actually made the sleeve positive was that they preferred to switch the battery positive in order to implement a charging circuit as it seemed to them, conveniently. Other than that, since the battery negative is not tied to ground, it is generally perfectly easy to have the negative switched.
Now recent computer do have an "insert detect" on the 3.5 mm "phone" jacks used for audio functions and that may be on the ground side or entirely separate and could be NC, NO or C/O as it suits them.