Protocol Options

Different protocols support different features. The details page of each protocol gives information specific to that protocol and its sub-protocols, including supported features, channel assignments, and any extra information.

Below are brief explanations of the features which protocols may have.

Protocol Features


Auto-bind protocols bind automatically when the radio and receiver (or model) are powered on.

In OpenTX, enabling the Bind on Channel option in Model Setup disables binding at power-on, and instead requires an input to be configured to initiate binding.

See the Binding page for more information about auto bind protocols and Bind on Channel.

Channel Re-mapping

Channel re-mapping automatically re-maps channels to the order required by the protocol - it assumes that the order specified in the Mixer or Outputs matches the expected channel order of the MULTI-Module.

Channel re-mapping is enabled by default for protocols which support it.

As of MULTI-Module firmware v1.3.0.45 and OpenTX 2.3.3, channel re-mapping can be disabled for a model by checking the Disable Ch. Map box in Model Setup.

Unless channel re-mapping is disabled in Model Setup, the channel order on the radio must match the expected channel order of the MULTI-Module (AETR, by default).

See the Channel Order page for more details.

pageChannel Order

Extended Limits

With normal limits, the range of all outputs is -100% to +100%. Enabling Extended Limits increases this range to -150% to +150%.


Failsafe settings determine what the receiver will do if radio communication is lost. The receiver is configured using settings sent from the radio as part of the radio transmission.

Configuring failsafe settings ensures that the receiver behaves in an expected way if radio communications between the radio and receiver are lost, for example by reducing throttle to -100%, or activating a return-to-home (RTH or RTL) function in the flight controller.

When configuring and testing failsafe, do so with the propellers removed, in case the motor(s) inadvertently start.

Protocols which support failsafe:

Failsafe Mode

Receiver Behaviour

Not Set

Failsafe not configured.


Hold the last values received before radio communication was lost.


Use the radio to configure specific values for the receiver to use.

No Pulses

All channels go to their minimum values.


Use values configured on the receiver using the receiver's configured failsafe settings.

OpenTX will warn if the failsafe option has not been selected for a protocol which supports it.

Receiver Match

If a protocol supports Receiver Match, it is enabled by specifying a unique Receiver Number (RX Num) for each model in the Model Setup page, before binding the receiver. If the Receiver Number is changed the receiver will need to be re-bound to the radio.

Receiver Match can be disabled by assigning the same Receiver Number to all models. Receiver Number 0 is typically used for this purpose.

See the Receiver Match page for more information.

pageReceiver Match


Telemetry enables the model or receiver to send information back to the radio,. Common uses are sending signal strength (RSSI) or flight battery voltage data so that it can be displayed on the radio.

Telemetry information is dependent on the protocol, model, receiver, or flight controller, and even if the protocol supports telemetry, the model may not be capable of sending it.

Telemetry is also used to send information about the MULTI-Module (such as firmware version and channel order) to the radio.

All MULTI-Module telemetry, including sending module version and channel order information to the radio, can be disabled by checking the Disable Telemetry box in Model Setup.

Do not check the Disable Telemetry box in Model Setup to eliminate telemetry warnings when using DSM receivers with short-range 'fly-by' telemetry. Check Disable telemetry alarms on the Telemetry page instead.

The Disable Telemetry setting is intended for use in FrSky radios where it is necessary to disable MULTI-Module telemetry from an external MULTI-Module in order to allow telemetry from the internal module.

Option Value

The Option Value may be used differently by each protocol. The use of Option Value is documented in each protocol's details page.

For a protocol where Option Value has defined use, OpenTX will typically display it as a named field, such as RF Fine Tuning.

Low Power Mode

Low Power Mode reduces the transmission output power of the MULTI-Module to approximately 1/10th of normal output. It can be useful for:

  • Short-range testing (the power output is similar to the Range Test option)

  • Operating in an environment where reduced RF output is needed

  • Operating 'toy grade' models which normally use a low power transmitter and do not cope well with full power signals

Low Power Mode significantly reduces the range of the MULTI-Module

OpenTX will warn when a model is selected which has Low Power Mode enabled.

Last updated