FrySky's smaller, lighter, redundancy system.
Building redundancy into our RC systems not only makes them safer but also helps to protect our investments. The FrSky Redundancy Bus-10 brings an added measure of insurance and reliability to the FrSky RC system. It gives us the ability to integrate dual receivers and dual power supplies into our control systems. The result is then, that the Redundancy Bus (RB-10) has a spare control signal and a spare power supply to rely upon in the event of a malfunction. The RB-10 also supports the S.Port telemetry system and its sensors as well as SBUS. Last but not least the RB-10 monitors all 8 servo output channels for overcurrent and overvoltage conditions, and will limit those outputs to protect your servos in the case something goes awry.
If you would like to peruse the manual click here.
Note : You will need to solder the battery connectors of your choice to the RB-10's pre-tinned solder pads.
Warning: Please do not use analog servos with this device. While they may work for a little while, they will probably burn out within a few minutes. Only use digital servos.