I can not speak for all models of the receivers but; the Futaba 127 will short out the battery if you plug it in backwards into the battery slot. If you plug it into any other slot, no harm--just won't work--but thelead that is normally the signal lead (in inside pin) is shorted directly to the center pin (the positive lead) by copper lands on the receiver printed circuit board on the battery slot only.
This results in a dead short accross the battery if you plug it in backwards resulting in lots of smoke and burned out wireing. If you doubt this, just remove the case and take a visual check.