[Discuss] OT? "standard" DC power connectors

[Bill Bogstad]

In thinking about the discussion here, I realized that there are
several ubiquitous "standard" DC sources/connectors:

5V DC via USB
9V DC via 9V battery connector
12V DC via cigarette lighter  (not sure if polarity is specified for these)
combined 5V & 12V via old style disk drive power connector

I'm not saying that these are good for general use, but they certainly
are well known with connectors being dirt cheap.

Bill Bogstad