I believe somebody made a neon matrix ROM -- have an electically rectangular array of neons with some present, others not. By applying suitable voltages to the X and Y wires, a particular location is addressed and the neon there fires (if there is a neon at that location), but none of the others do. There was a photomultiplier aimed at the neons to detect the light flash. I seem to rememebr there was the well-known problem that neons in the dark don't fire reliably, which was got round by firing another neon just before addressing a location (this neon could have a high enough voltage applied to it to make sure it always fired reliably) and then ignoring the extra pulse from the PM tube. Of course this did not use the memory property of the neons themselves -- the data was stored by which neons were fitted. I wish I could remember which machine used this. Maybe something like EDSAC 2? -tony