That is really fascinating, thanks. That's the vacuum my aunt had (early to mid-90's) which I used and studied. Hers did not have the power switch, just the red reset button. She and Mom went shopping one time and I got it out and used it. I was shocked it had so little suction. I tried adjusting the valve both directions to no avail. I took the hose off and peeked into the port and I could see a mass of dirt, fuzz, string, and hair peeking back. I stuck my finger in and it hit resistance right away. The filter bag was jammed solid all the way to the opeining port. I assumed at the time that was why it had so little suction. I wonder now why the machine let that happen. Why didn't it shut off? Maybe the auto shut-off didn't work anymore or maybe it's hose was leaky. Always wondered about it but a few years later I got to experience a Renaissance in an Electrolux store and it dispelled any qualms about weak suction. Love Electrolux info on this site.