wrote:

?ATTENTION?: DC Plug Polarity: inner Positive(+), outer Negative(-).
If You Are Looking for an Opposite Polarity Charger, Please Search
B01IVPXV38 or www.amazon.com/dp/B01IVPXV38.

Your solution comes in two pieces. _____
/ \ +----+
+--------+ / \ | ----- Barrel
--- Adapter xxxxxxxxxxxxxxxxxxxxx| O o | | -----
--- \ Female/ +----+
+--------+ \_____/ | | == Male pins

That is a "polarized" adapter. The matching plugs have
(+) and (-) written on the side of the L-shaped thing
that plugs into the end of the adapter.

The two holes are different sizes, so it only plugs in
one way. The male pins are two different diameters.
The female portion has one hole bigger than the other.

Because it only plugs in one way, the product delivers
"Center Positive" by default. Before buying a keyed
product like that, you verify your KVM is "Center Positive"
before buying a Center Positive (keyed style) adapter.

*******

The other kind of adapter (ones at RadioShack) have identical
sized holes on the Adapter end piece. _____
/ \
+--------+ / \
--- Adapter xxxxxxxxxxxxxxxxxxxxx| O O |
--- \ /
+--------+ \_____/

As a consequence of this choice, the L-shaped piece that
plugs into that, goes *two possible ways*. It can go the
right way and the wrong way, so to speak.

If you were to buy such a thing, you'd use your multimeter
to verify the center pin was positive with respect to the
shield. This must be done with some care, to avoid
unnecessarily shorting out the adapter. This is the
kind I own.

Because of the added flexibility, I can have "Center Positive"
or "Center Negative", just by rotating the L-shaped
piece before plugging it into the adapter.

Such an adapter is only recommended for those who
like multimeters and have some grasp of the basics
of "electricity" :-) Not many pieces of electronics
have polarity protection, but some do.

*******

Since you bought the top item, you won't have to worry.

When you get it, verify it's "keyed" by means of the
two hole sizes, and that the plug only goes in one
way. (When the L-shaped meets the adapter end, only
one way of inserting it.)

The product is keyed for "Center Positive". As long
as the label in the KVM plastic shows "Center Positive"
as well, you're all ready to go.

I still like to use my multimeter, because I'd
a curious individual who verifies lots of stuff.
That's just the way I am.

Paul