A technique we use is to give the nozzle-man a thumbs up when within 200lbs of target, on the S76B, that way he knew to adjust the flow rate and watch carefully to see the cutoff signal, and/or not overflow. Works for us.
I would be shy of using any communications equipment near an open fuel port during refueling. I've only seen one refueling fire. It was precipitated by static from the nozzle not being grounded prior to fitment to the fuel port. The rest is obvious.