I learned another one today: BEC - Battery Eliminator Circuit.

From [link=http://www.fxaeromodels.com/product_info.php?cPath=203&products_id=3156]FXAeromodels[/link]:
"An electric helicopter has a large battery which powers the main motor. The voltage of this main motor battery is typically higher than can be used by the receiver and servos which normally require 4.8 volts. The BEC lowers the voltage of the main battery pack to 4.8 volts to power the receiver, gyro, and servos, eliminating the need for a separate 4.8 volt receiver pack."