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Failsafe is a receiver function that allows the user to set positions to move the servos to if the signal from the transmitter should be lost. The receiver will hold the servos at the last received positions briefly in case the signal returns, and then enters the failsafe condition. If the signal should return, then the receiver will return to normal operation.

Most transmitters allow you select between two options on a per-channel basis:

  • Position hold: The servos remain in their last received position.
  • Failsafe position: The servo is commanded to a failsafe position set by the user.

By default, most transmitters will be set up to hold position for all channels. It is good practice (and required by many aeromodelling associations) to, at a minimum, set the throttle failsafe to close the throttle in the event of signal loss.

Spektrum failsafe positions are set to the position of the controls at the time that the receiver is bound to the transmitter. Typically this means that after the user has configured the transmitter for their new model, they must re-bind to set the failsafe positions. These failsafe positions are used if the transmitter signal cannot be found when the receiver is first switched on. If the transmitter signal is subsequently lost, only the throttle channel will go to the failsafe position; all other channels will hold their current position.

Many PCM receivers support failsafe operation; in this case, the failsafe positions are broadcast periodically by the transmitter. In general, PPM receivers do not support failsafe, except for some unusual aftermarket receivers.

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