Thanks Sluggo,
That gage in on the upper part of the panel and fairly small, like Gregor said, they felt the pressure on their ears then the FE looked at the panel.
I was on submarines, and when we popped the hatch you could definitly feel it on the ears. Not quite the same as what an aircraft would feel.
As a side note, my dad was a FE on C-121's, C-118's and C-130's. He said that they would rais the cabin altitude and reduce the O2 bleed to put the passengers to sleep :-)
Also Sluggo, Victor airways are not just for VFR, In a IFR 172, you will not be assigned to a Jet route, but assigned to a victor airway. But you knew that ;-)