The push button on the top of the TX is used both for binding, and to store Failsafe into the receiver.
When the button is pressed while the TX is powered on the unit is binding. When the TX is in normal flight mode, the button is used to store failsafe.
The different modes of failsafe in the receiver manual are:
All kinds of FAILSAFE storing and testing should be carefully performed with the plane firmly grounded.
It’s normally good use full failsafe style to program the plane to shut of motor and turn slowly to the left side. Some FPV/UAV systems can use other settings; the user should know what is best for his usage.
Always test if it’s working as expected before a flight – Test if recall the wanted function and recover again when the TX is powered back on.
The normal kind of failsafe is one set of servo positions stored in the receiver. This setting will be recalled and used when the radio signal is lost for about 1 second. To store a set of servo positions, push and hold the button for 1 second and then release it. Please be sure not to push it again the next 5 seconds.
The “Sequential” works almost the same way. The difference is that you push the button again under 5 sec after release to store the next set of servo positions. This can be repeated 3 times to use all 3 servo memories. They are recalled in same order as stored, and when/if the radio signal is recovered the return to normal flight is the reverse way.
The procedure is as follows:
The radio signal is lost - recall 1, recall 2, recall 3.
Radio signal back, - recall 2, recall 1, live.
It will run scan mode which means, if a good package is received while it is in recall 2 state, it will go directly to recall 1 and then back live. Each recall state take about 0.3 seconds then it recall the next state. This special kind of failsafe can be used to handle special features on some multi rotor flight controller boards to activate the RTH or safe landing procedures, depending on how you moved your switches while you stored the fail safes.
The “None” is when the receiver doesn’t have any positions stored at all. In this way nothing will be recalled and it will simply hold last known good position of all servos. To clear the failsafe memory, hold the button for 5 sec.
A little side note on failsafe storing. The Receiver will lose radio link and recall failsafe settings while you activate a storing. The reason is the kind of memory used for this is a bit slow and while the CPU waits for the saving it’s not able to maintain a perfect hoping sequence. This is perfectly normal but it is not normally seen when you only store one set of positions, since the values you recall while you hit save are mostly the same as your active positions.