turn (SWITCH)
verb [always + adv/prep]
to use a control to switch (a piece of equipment) on or off, or to adjust it to change the amount of what it is producing
Please turn off/out the lights when you leave.
Who turned my computer on/off?
Turn the TV down (= make the sound quieter) -- it's too loud.
Turn up the volume -- I can't hear what they're saying.
switch on/off obj, switch obj on/off
phrasal verb [M]
to start or stop (a device powered by electricity)
She switched the light off.
Switch on the video camera, please.
From Cambridge Dictionaries - American English