The RVP70 is used to prevent damage to RC equipment, speed controls, chargers, anything that you connect up to a battery.
It works by connecting it across your devices battery input, e.g. speed controller battery wires. You then plug your battery pack into the RVP module instead of the speed control, it checks to make sure that the battery has been connected correctly, green light for good, red for bad! If it lights up green, the speed control will work as normal. If it lights up red, you need to swap the battery wires around. Had you not used the RVP module you would more than likely have damaged your speed control by inadvertently connecting your battery backwards!
The RVP70 has a 70Amp current limit so it is suitable for use with all chargers and speed controls with up to a 70Amp limit and is also 100% waterproof!