The RF Board is a small PCB that plugs into the front of the motherboard. It is responsible for wireless controller connection and the front panel buttons/LEDs.
Original Xbox 360
Codename Argon. Used on all Original Xbox 360's except for Tonasket. Multiple revisions exist with minor differences.
Known as xFreedom. Used on Tonasket.
Xbox 360 S
Xbox 360 E
The RF board on the Xbox 360 E is split into two PCBs, connected by a ribbon cable. The main PCB connected to the motherboard contains the primary functionality. The smaller secondary PCB - attached to the faceplate - contains power button, eject button, sync button, and Ring-Of-Light LEDs.