Vacuum tube exercise equip at the gym?

Anyone ever notice anything unusual about Cybex equipment at the gym. Specifically, the Hip Abductor and Hip Adductor machines. I belong to LA Fitness and it looks like these 2 machines have an input tube at the bottom of it next to the belt. There it is a dark glass input tube in some kind of tube socket, don't have any idea what this glass things does, but it looks exactly like a 12ax7 or something. Any ideas? Have you ever noticed this?

No other Cybex machines have this tube thing except for these 2 machines.
Do you experience lush highs but still suffer from a flabby base when working out? ;}
Well now I'm curious. I think we have Cybex at my gym, I'll have to look. Is it a metalpin to preventover-rotation of part of the machine?
It doesn't look like it has any function at all. Only the top 1/2 of the tube is visible, the rest of it is inside the tube well - its a black glass tube.

Tom - its newer gear so you don't have the lush highs or flabby base like you do with classic exercise gear...but like all tube gear still very sweet & euphonic :)