Hi Uli. Press the switch for several seconds until the indicator light on the front of the unit goes off or on. It works for me. Otherwise very satisfied, except perhaps that it takes a while to wake up from the "sleep phase". Hope I was able to help, greetings. Dominik.

Same as Dominik, he described it perfectly. Press for 3-4 seconds, then it goes off. A short press is enough to wake it up.