Product review (4 stars): Great Little Machine
Like others, I read the available reviews but didn't glean any info on how the machine was turned on or off. They mentioned a 'timer' but what the .....?
So, here is the 'skinny': The 'Timer' mechanism is 'spring-wound' and doesn't care if the machine is plugged in, or not. Once set, power is applied and the motor cycles between clockwise motion and counter-clockwise motion with a few 'ticks' of the timer in-between.  This is so the motor doesn't slam between one way and the other. Less wear and tear. This is 'good'.
What might be bad is if you turn the 'Timer' counter-clockwise. Don't. You might screw it up. If you want the machine to turn off just unplug it -- and let the 'timer' run its course. Much safer.
Otherwise, it's an amazing little machine. I've added different hoses with 'quick-disconnects'. Makes life easier. I'm happy with it, so far. Let's see how long it'll last.