FlySky FGr4S 2.4GHz 4-Channel AFHDS3 Receiver. The FGr4S is a four-channel, two-way receiver utilizing the AFHDS3 (Third Generation Automatic Frequency Hopping Digital System) protocol. Featuring dual antennas, a PPX6 nano waterproof rating, and a compact, lightweight design, this receiver supports four Newport function interfaces. These interfaces can be customized for various signal types, including i-BUS2, S.BUS, i-BUS, and PPM. Additionally, the FGr4D can function as a PWM converter, making it ideal for use in model cars or boats.