This article was pointed out to me by Jeff L. and it is interesting in that it
explained the Chinese standard, the EU standard, and the Apple standard of USB
charging circuits:
http://blog.curioussystem.com/2010/0...vice-charging/

Apple, being different, used voltages for their charging circuitry:
- low current: 2.8 volts across Data(+)
- high current: 2.0 volts across Data(-)

The EU used a 1/8W 200 ohm resistor, & the Chinese simply short the data pins.

The five 1/8 watt resistor "hybrid" circuit in that article nicely explains how
a USB charger can work *either* for Apple (voltage) or EU (resistance) or
Chinese (short) charge circuits; but not all three at the same time!