I am trying to find information on this as well, and I hope someone replies.

I'm also intrigued... googled it and came across this page. Someone's gotta know??

This is the answer I got from the technical analyst with the Resolution Expert Center (REC) at Dell assigned to your Optiplex 7040 Micro service request.

Here are some steps I have found for USB Wake Support:

1.       In “Power Management” setting of BIOS please Enable “USB Wake Support” and Disable “Deep Sleep Control”

2.       Connect Keyboard or Mouse to Smart Power On Connector port

3.       Disable Fast Startup in OS.

Search for and open “Power options” in the Start Menu.

Click “Choose what the power buttons do” on the left side of the window.

Click “Change settings that are currently unavailable.”

Under “Shutdown settings” make sure “Turn on fast startup” is disabled.

I plugged Logitech wireless keyboard+mouse dongle into the USB port, shutdown the computer, and

and typed "Alt+P" (which is Lenovo Thinkcentre desktop Smart Power On keystroke), and it powered up.

Hope it answers your curisity.

If you plug a wireless dongle, keyboard,or mouse into that port then you can enable the computer to power on or wake the computer simply by pressing S3,S4, orS5 on the keyboard

@Nickn99

You wrote "pressing S3,S4, orS5 on the keyboard". Did you mean SHIFT 3, SHIFT 4, SHIFT 5 or F3, F4, F5? Or was it something else completely (if this last choice, please elaborate/clarify)? Because I've never seen a keyboard with S3, S4 or S5.

Still no real answer to this question.