Hello,
That access, is the potentiometer, to change from ( CE to FCC ) modes.
CE= conformite europeenne ( French for / European conformity. )
FCC= federal communication commission.
CE mode gives you a lower power range output on your remote, giving you about 300 meter range ( Europe standards )
FCC mode gives you a greater power output on remote, giving you approx 500 meter range ( USA standards )
If your remote is in CE mode, you'll get 1 beep when turned on.
If your remote is in FCC mode, you'll het 2 beeps when turned on.
Hope this helps!
Take care, Fly safe!
J Dot