On Wed, 22 Feb 2017 10:32:28 -0800 (PST), Weatherlawyer
wrote:

On Wednesday, 22 February 2017 16:58:30 UTC, Andy Burns wrote:
Weatherlawyer wrote:

I have a Dell notebook and am trying to get a multi settings charger
to power it up.

Model?
Dell Latitude D400

The horizontal lines only indicate that it's DC rather than AC, they
don't say anything about polarity.

Is it one of the Dells with three connections to the 19V PSU?

It is q 11.1V battery IIRC.

Rather than supplying power over the outer surface of the barrel and a
centre pin, they supply power over the outer and inner surfaces of the
barrel connection, with a slim data pin in the centre.

Without any connection on the data pin the laptop is likely to complain
about incompatible charger and work in "limp" mode where it will run at
slowest speed and may not charge the battery at all.

I dare say there is a reason for that but I would never find out and am not likely to buy another Dell. Ever!

Probably the same reason printers do some sort of digital masonic
handshake with the ink cartridges.