"David R.Birch" wrote:
SCUBA tanks used to have a J valve that stopped the air when you had
about 10% left, you pressed the valve and got ready to surface. Now
it's more common to have a visible pressure gauge, but you have to
remember to look at it.
David

Ah old school there David. I never used on but I am told that one
major failing of this design was you had to toggle a valve lever to
the reserve position otherwise it wouldn't retain reserve pressure.

I think my favorite work project of the 3 dvds was replacing a tv
antenna at the top of a 2000 ft cable stayed mast.