How to activate RC failsafe?

Greetings! I’m asking for help!!! How to make it so that when communication between rx and tx is lost, the failsafe is turned on, the device remains in arm and flies according to the last values ​​given by tx, and after the communication is restored, the control returns, how to do it? Is this setting possible?

There is comprehensive info here. Read thru it:
Failsafe

Set up the radio failsafes. Typically when there is a radio failsafe it will initiate RTL, but you can adjust that with the FS_OPTIONS.

https://ardupilot.org/copter/docs/radio-failsafe.html

i understand right?Continue if in Auto on RC failsafe - its remember last values which which were before failsafe turns on and continue to flight???

It totally depends on how you configure it. It’s up to you. Read the links we provided.

Use Mission Planners simulator to run different scenarios so YOU know what to expect.
SIM_RC_FAIL is what you want to change.