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Pressing the Power button will put it to sleep or power saving mode rather than turn it off. It will also goes to sleep (power saving mode) after 30 seconds of last print job. It will wake automatically when it get a print job from a computer or another device or by pressing the Power button.
This machine is designed this way. If you want to turn it off completely, then you have to put it to sleep first either by pressing the Power button once or after 30 seconds of last print job. Then press and hold down the Power button until all lights goes off or switch off the power button on the power outlet or unplug the cable.
If you have have any questions or would like any additional information, please don't hesitate to ask.
If this is not the information you are looking for, please don't rate me bad or poor. This is how Samsung designed it. Please let me know if you need any help