I'm not sure of how much this belongs in Wikipedia, but I'll post it here because I was trying to find the coaxial power connector details online.
There's both a mini-USB plug and AC adapter jack at the bottom of the Zire 72. There's no PalmOne "Universal" Connector like on the 71, so it won't work with a lot of other accessories for the palm. The Zire 71, however, *does* charge through the mini-USB, but it appears to charge slower, and the green charging LED, located on the top-left of the unit, does not light like when you use the AC adapter. Also, the automatic "stay-on" feature (setting) does not function when charging via USB
The AC adapter (aka "wall-wart") says it is rated at 5.2 volt DC with 500mA and the center of the coaxial power connector is positive. With my DMM, I measured 5.66 volts with the connector not plugged into the Zire 72. The connector is most likely a 2.35 mm OD × 0.70 mm ID (Radio Shack Adaptaplug Size A, also called EIAJ-01, but I'll try to update this to confirm.