Not used "BEADWINDOW" since my days on OP BANNER when passing fuel delivery details over a phone line via a MATRIX and the person on the other side of conversation then proceeded to recite the meaning (dates times location and Qty of fuel to be delivered) in open speech. I loudly said "BEADWINDOW" more than once and they asked what it meant, I just said the ONLY response should be "Roger OUT" and terminate the call. Had to arrange the whole delivery from scratch again. It seemed only a few people knew its meaning if I recall rightly.