Pardon my ignorance, but what is the difference b/w PIN 7 on the black plug (8 pins) & PIN 16 on the blue CD plug (8 pins)

According to the bentley
PIN 7 on the black plug is "Battery, positive (B+) supply, terminal 30"
PIN 16 on the blue is "CD changer - Power supply, positive (B+) supply"
Is there a difference?

I initialy wired my DVD player & audio/video converter to PIN 7 on the black plug, but it appears to be contantly draining power from the battery even when the radio is off.

I'm trying to find an alternative, so that the DVD player and converter only use power when the radio is on.

I know that on the line out plug (yellow), PIN 6 is "Switched positive (B+) for amplifier" so I believe it sends power depending on whether the radio is on or off, but I don't have that plug to tap into.

I'm debating b/w conneting the positive wire to PIN 16 or PIN 17 on the CD plug. I'm under the impression that the CD player only gets power when the radio is on, but I might be mistaken, which makes me feels that I should plug it to PIN 17. According to the bently, PIN 17 is "17 - CD changer - Control signal". I'm not sure what that means...