What happens when disengaging the electricity generators on a B747?
This is how it works on all aircraft with a Constant Speed Drive (CSD) Generator or an Integrated Drive Generator (IDG) - doesn't matter who the airframe maker is.

When you press the disconnect button (the red arrow), the disconnect circuit is completed and the solenoid pulls the pin out of the pinion shaft (the blue arrow) which then engages the worm gear on the drive shaft (the green arrow) and causes that gear to disengage from the drive mechanism. This causes the generator to stop turning.

To reset the mechanism you have to pull the "RESET HANDLE". This drive mechanism is attached to the gearbox on the engine which means that it can only be done on the ground with the engine off