Does the electromagnetic pen need to work on a touch screen? Or can it work directly on the display?

This is a very good question, and it touches upon the core technological differences of modern touch devices.

The simple, direct answer is: an electromagnetic stylus must be used with a touchscreen that supports electromagnetic induction;

 it won't work on a standard capacitive touchscreen.

The following explains the reasons and the differences between different technologies in detail:

1. How the Electromagnetic Pen Works

The electromagnetic pen itself does not require batteries (as most passive solutions do). Its core is a resonant circuit. 

A dedicated electromagnetic induction board is integrated beneath the screen.

How it works: When an electromagnetic pen is brought close to the screen, the sensor pad emits an electromagnetic signal, 

which is received and resonated by the circuit in the pen body, and then a signal is reflected back.

· Positioning: The sensor pad uses the received return signal to accurately calculate the coordinates of the pen tip, 

pressure, tilt angle, and even whether the "eraser" at the end of the pen body is in use.

· Key Points: This is a passive electromagnetic induction technology; there is no physical contact between the pen and the screen; 

instead, the pen and the screen "communicate" through magnetic fields.

2. What is a commonly used "touch screen"?

When we refer to a "touch screen," we usually refer to a capacitive touch screen.

· Working Principle: It utilizes the human body's electrical current induction. When your finger (a conductor) touches the screen, 

it affects the electrostatic field on the screen surface, thus detecting the position.

· Relationship with Electromagnetic Styluses: Ordinary capacitive screens cannot detect the electromagnetic signal from an 

electromagnetic stylus. To enable capacitive screens to function with a stylus, active capacitive pens have emerged on the market. 

Their tips are made of conductive material, simulating the touch of a finger. However, these pens generally lack pressure sensitivity 

and have lower accuracy.

So, back to question:

· Does an electromagnetic stylus work on a touchscreen?

 Yes, but it requires a special touchscreen with an integrated electromagnetic sensing layer, not a standard capacitive touchscreen.

· Or can it work directly on the display?

 No. An electromagnetic stylus won't work on any standard display without a built-in electromagnetic sensing layer, whether 

it's LCD or OLED. It relies on a specialized sensing layer underneath the screen, not light emitted by the screen itself.

You can think of it this way: devices that support electromagnetic pens (such as high-end drawing tablets and 2-in-1 laptops) 

actually have an electromagnetic induction board "sandwiched" behind the display. The electromagnetic stylus communicates 

with this "board" rather than directly with the "screen" that displays the image.