The "smart" pin (center pin) on laptop power supply connectors is used for the purpose of the computer being able to determine the amperage (or wattage, if you prefer) of the 18.5 volt power supply that is plugged in to it, so it does not exceed it's capacity, especially when the computer is running AND charging the battery (or batteries) at the same time. I found a thread relating to this (topic#137840), but it is closed, and it did NOT provide the answer that I was looking for, anyways. I believe that the pin voltage will vary between around 5-6 volts to maybe 10-12 volts. The higher the voltage, the more current (amps) the PS can deliver. If the pin voltage is outside of this range, or the center wire is broken off at the connector, the laptop will not run off of it (at least for HP/compaq laptops). I run into the broken off center conductor wire scenario regularly. I suppose that is the one that always breaks first because it is the thinnest of the wires going to the plug, from the PS. I use one of those 6.7 amp brick-sized power supplies on my compaq 6715b, because it has a secondary battery attached to it (underneath). But the interesting thing is that I had the PS connected to a Dell laptop once, and it would run the computer, but refused to charge the battery. When the PS was plugged into it, a message would come up on the screen stating that the type of the PS could not be determined. Assuming that ALL brands of laptops now use the same type of power connector, is there any sort of "standard" among manufacturers that correlates center-pin voltage with PS capacity, or is it wide open to whatever they decide? If there is a standard, could someone please provide me with the link to some sort of "correlation table" showing center pin voltage vs. PS capacity?