knob...
Hello guys, I've noticed the adjusting knob also on other european Electroluxes, starting from the late 60s, but especially in the Seventies it became a very advertised feaure: AUTOMATIC was the most preferred word. Electrlux canisters featured this device that, depending on the type of dirt you were picking up, automatically shut the motor off and opened the front of the machine when airflow passing trough the bag wasn't enough so the bag was clogged and needed replacement.
People usually kept the feature shut off because it was very sensitive and sometimes it asked for bag replacement when it was almost fresh, depending on the model.I've also experienced that on an older model with a newer and more powerful motor, the feature would stop the motor everytime you turn it on.
In 1980 or so, this feature was replaced by a "full bag indicator" with 5 positions ( model D 728), and later by a simple full bag indicator lamp, much easier to understand!
Take care all!
tommy