Andy Burns wrote:
Jon Elson wrote:

Is this the triple-coaxial plugs they use on Dells? The outer barrel is
gnd, the inner side of the barrel is +19.5 V, the center pin is some
resistor or something that classifies the power supply's capacity.

More than just a resistor, I think it's a 1-wire bus.



But whatever it is, it's not too complex. My non-Dell laptop supply
has a special adapter for Dell laptops. It's a bit larger that the
other plugs and it does fool the laptop into charging.