Ceppo,
The Avweb site is a good one for information. Couldn't find an answer for your question about electrically actuated variable pitch props on it, so...
The entire motor is mounted in the prop hub & rotates with it. The blade's pitch change is relative to the hub so the output of the motor is connected to the mechanism that moves the blades.
Now the problem is how to get electrical power to the motor since it's rotating along with the hub & the aircraft's electrical system is not.
This is done using a brush mechanism in a similar manner to the brushes used in some electric motors/alternators etc.
All that needs to done is to mount a conducting ring on the hub that is electrically insulated from the hub. A wire connects to this ring to the electric motor to carry the current. An electrical contact from the electric system is mounted on the airframe in a such a way as that it continually brushes against this rotating surface.
Two rings & brushes are needed, one for electricity to flow in, and for it to flow back out.
This mechanism is also used for props that use electrical power to heat the blades for anti- or de-icing purposes.
[This message has been edited by Tinstaafl (edited 14 June 2001).]