Furious True-D 4.0 On/Off functionality

Hi, im using the above receiver on my DJI Goggles and a Digidapter from BDI. the products page states the following: Power On / Power Off Functionality To Conserve Power & Reduce Thermal Loading.
after trawling the internet i understand that this function is activated direct on the fatshark goggles and/or on the receiver itself. as i have the DJI Goggles then i need the latter option.
but ive no idea how to use this function?
its certainly not clear in the menu and i cant find a specific 4.0 manual online.
any help would be great.