The RX4R is a standalone receiver with all the functions of the original X4R-SB. It features 4 PWM outputs with high precision and low latency 9ms less than that of the X4R in high speed mode. The RX4R also supports the redundancy function, which means you can add another receiver as a back-up in case the first one fails. Last but not least, the RX4R and the whole RX-line has a 40% increased operating range compared to the previous X series receivers.