In this RC transmitter tutorial, you will learn how to enhance the security of your drone-transmitter connection with help from the FrSky RB-40 redundancy module. The growing popularity of drones has brought on a demand for improved transmission security in order to avoid the loss of drones flying in populated areas, on commercial operations like delivery and surveillance, or flying as a hobby.  

Redundant systems: what are they, and why do they matter?

Redundancy is a concept that involves doubling the critical components or functions inside a system with the express goal of increasing reliability. Let’s say that a battery disconnects or an ESC fries while flying a drone. Without a redundant system, that drone is coming crashing down. With one, on the other hand, no critical component is solely responsible for an entire system, so there’s always a backup.

The FrSky RB-40 Redundancy Bus is a unique central module capable of operating two different receptors and batteries in order to afford you peace of mind during a flight day. The RB-40 can be programmed with triple redundancy, adding a multiplex port (RX3 IN / SBUS OUT) and a set of standard XT60 plugs to provide complete safety and an efficient power supply.


A good option to avoid interference issues with the FrSky redundancy system is the capability of creating a double-frequency system for greater security. To achieve this, you can add an R9 module in the back of your FrSky transmitter and plug in an R9 receptor in the SBUS IN port. Now, you can make use of your transmitter in both 2.4 GHz and 900 MHz frequencies.

Safe and easy to install

Installing the RB-40 is extremely simple: all you need to do is connect the receptors through the SBUS IN ports in the Redundancy Bus. This way, should the main receptor receive patchy communications, the transmission will switch over immediately to the second receptor if this one boasts a better signal.


The receptors can be connected in one of two ways. They can be either linked up in series or connected directly to the RB-40. The image below shows a schematic describing how to link up the receptors and sensors. To take advantage of the multi-access receptor bindings with the same ISRM module, modify the UID for different receptors.

What else does the RB-40 have to offer?

The RB-40 offers the same reliable attributes from the previous Redundancy Bus, in addition to boasting new resources to attend the demand of a growing variety of users, like 24 PWM channels with safeguards against high-tension overloads in every OUT channel, and channels 1 through 8 are also equipped with current sensors.


The RB-40 also supports FrSky’s proprietary Smart Port telemetry for their transmitters. With Smart Port, you can receive feedback on telemetry’s tension, current, power consumption, altitude, and much more. Additionally, thanks to the diversified sensors, it can also be used as an alternative to an S or GR-series receptor.

The new Redundancy Buses from FrSky also presents an NFC switch and automatic data recording functions. The non-contact NFC switch is an external device that allows you to turn the power on and off on demand without the need to personally handle the batteries. After the power is turned on, the black box function is activated automatically and starts recording data and backing up flight details.


Another feature is the LCD display, sized similarly to the display in the X-Lite series transmitter. Browsing and configuring telemetry data is even more convenient with the scroll button. And yet, with all these features, the RB-40 weighs just 260 grams, the result of a design composed of carbon fiber and aluminum.

Even though the redundant system makes the drone fly a little heavier, few pilots will complain about the added weight considering how much this system works to protect their equipment. On top of that, the RB-40 also offers a built-in gyroscopic sensor with stabilization functions, improving the performance and precision of the maneuvers with your drone.

The drone market is in constant development, and safeguarding drones against damage to themselves and to people around is a large priority. It’s for this reason that redundant systems make all the difference, introducing failproof mechanisms to drones and thereby greatly increasing their lifespan and the security of flight days. The FrSky RB-40 Dual Power can be acquired on