Thx Alain !

My Rx have not a fail-safe. When signal is missing the pulse is 0 .
I use for test usually RC , not Graupner or Futaba JR

I changed my code, but the same:

varb var byte
varb = 0
pause 200

init:
pulsin portc.2 , 1, varb
if varb < 140 or varb > 160 then init
if varb > 140 and varb < 160 then goto beep
goto init