It's the same as old VW beetles which had a reserve gas tank. When you ran out of gas you opened a valve and you could limp to a gas station
In scuba diving there used to be "J-valves". When you had 50 bar left in the tank they would cut out. Then you would pull to reenable your air and return to the surface. Unsurprisingly they are no longer popular.
In scuba diving there used to be "J-valves". When you had 50 bar left in the tank they would cut out. Then you would pull to reenable your air and return to the surface. Unsurprisingly they are no longer popular.