Feret,
I think JEP was asking for an explanation of the fundamental principles......the system schematic on every aircraft type is different, and has its own quirks with regards to practical day to day operation. Also, I think you'll find the sidewall on most types a bit on the cold side. I'm not being antagonistic honest, but you talk of the 767, I could go on about the 747, 727 & L1011, but it doesn't explain the way it works........