From the Spektrum ix12 transmitter manual:
"Failsafe is configured when the transmitter and receiver go through the binding process. When binding an aircraft, always follow these steps to ensure the failsafe operates as expected in the unlikely event of a loss of radio link:
1. Move the throttle to the low or off position.
2. Set all other controls to the desired failsafe position.
3. Follow the receiver instructions to power the receiver on in bind mode.
4. From the iX12 transmitter Bind menu, touch and hold BIND until the transmitter reports it is binding.
5. When the transmitter indicates binding was successful, power off the receiver, according to the receiver instructions.
After the transmitter and receiver are bound, if the radio signal link is ever lost between the transmitter and receiver, the receiver immediately moves the aircraft control surfaces to the failsafe positions or holds position depending on the type of failsafe set during bind."