The signal was fine. When someone turns off the gas (isolates a FF for instance), the computer sees that the tank pressure dropped to zero. Unless it is on land, it isn't quite certain which tank that it locked onto when it sees significant tank pressure again. So, I locks into the last known reading and flashes fail. I knew that this was going to happen when I shut the tank valve as we ran into this with my dive buddies (who also use VyTec's) when they did their valve shutdowns for their IANTD Adv. Nitrox class.Wreck:The Vytec will only let you go six minutes without a pressure transmission before flashing that "Fail" warning. I guess with doubles emptying so slowly you wouldn't have noticed a slight decrease in pressure over several minutes.