Brother HL-3170CDW - Manual (Page 109)

General Information
103
3
Auto Power Off
3
If the machine is in Deep Sleep mode for a certain length of time, it will go into Power Off mode automatically.
To start printing, press and hold down on the control panel and then send the print data.
You can choose how long the machine must be in Deep Sleep mode before it goes into Auto Power Off mode,
by following these steps:
a Press a or b to choose General Setup. Press OK.
b Press a or b to choose Ecology. Press OK.
c Press a or b to choose Auto Power Off. Press OK.
d Press a or b to choose Off, 1 hour, 2 hours, 4 hours or 8 hours. Press OK or Go.
NOTE
The machine does not go into Power Off when the machine is connected to a wired or wireless network
or has secure print data in the memory.