The SPM4651T DSMX SRXL2 Serial Micro Receiver takes the original SPM4649T receiver and adds more value, functionality, longer control and telemetry link range. The SPM4651T uses our feature-rich SRXL2 protocol to give pilots a blazing fast serial data connection with up to 20 channels. SRXL2 is a powerful and open source communication protocol developed by Spektrum. It greatly improves bi-directional communication between the radio system and flight controller for added telemetry functionality and flight control configuration right from the pilots Spektrum Transmitter*, all over one signal wire.