How do printers detect the presence of paper?

Question

Printers

I am definitely looking for an inkjet printer to replace
1) Epson WF-M5190dw (manual feed tray and cassette feed tray).
They do not have paper sensors, they pull the mechanism first of the manual feed tray. If there is no paper, pull twice.
Then pulls the tray mechanism from the cassette feed. If there is no paper, pull twice.
2) HP M426dw Laser All-In-One (Manual Feed Tray and Paper Stack Tray) are also available. When printing, without forcing the mechanics once again, they take paper only from the tray in which it is.

How does a laser printer detect the presence of paper in the tray without jerking the mechanics? What is the name of this opportunity? We are looking for an inkjet printer with this capability.

Answer 1

I don’t know much about printers, but I can assume that there is some kind of optical control system there. She, in turn, checks the presence / not the presence of paper in the tray.

Answer 2

How does the laser printer detect paper in the tray

If you completely pull out the tray and fumble with your hand under the printer, you can feel for a small lever (sometimes called a "flag"), it rotates on its axis without effort (there is no spring, it falls under its own weight, and it is light) and depending on the thickness of the stack of paper appears in a different position.

What is the name of this opportunity?

Paper present sensor. But in the characteristics they may not write about him, even if he is. Of course, more expensive models are more likely to be available than cheaper ones.