Thought it might be opportune to explain the oxygen system.
The B744 has a gaseous oxygen system. This was the norm back in the 60s, all aircraft were like this. The oxygen generators appeared in the early 70s, I first saw them on the L1011 where they were standard on the pax system. They are now standard on most aircraft. Unusually the B777 can be seen with both systems depending on the airline.
Anyway back to the B744.
The crew and pax systems are separate. The crew has one or two bottles, the pax side has a row of bottles, the total number depends on the airline fit. All the bottles are filled from one charging point. NRVs separate the crew and pax systems. The pax bottles are all connected to a common main through individual regulators. Loss of one bottle would not affect thesystem, unless the regulator was damaged when the whole system pressure could drain away.
The B744 pax system has two modes, therapeutic and emergency. Therapeutic is selected by a red guarded switch in the flight deck (looks the same as the manual on switch!) A none-surge flow control valve introduces oxygen at about 2psi into the pax supply. Separate masks can be plugged into this main.
If emergency is selected manually, or automatically via a cabin altitude switch, the surge flow control valves introduce oxygen at about 16psi into the same main. This higher pressure opens the PSU doors and allows the masks to drop. Each mask is individually actuated by pulling it down which releases a pin from the supply valve and oxygen starts to flow. The ring main pressure drops to 2 psi after actuation. Oxygen will continue to flow from each actuated mask until the system is switched off.
So, masks are dropped by oxygen pressure (the door latches are not electric)
The whole system is one big ring main.
All the pax bottles feed the same main.
Pulling the mask to your face should be sufficient to pull out the pin, but there is a streamer there that says pull on it.
Oxy generator systems are different in that the doors are opened electrically. Pulling on one mask starts the flow of oxygen to all masks in the same box.
The system cannot be stopped once started.
(Also once it is used it takes forever to replace all the generators).