Long. long ago, the only way to interact with a computer was through a stack of punched cards. Then, technology improved so that we could now use a mouse and a keyboard.

In the last 10 years, we took another technological stride, and now, we use touch to interact with computers. In fact, touch is the de facto technology for ebook readers and smartphones.

Even though it’s very easy to use touch controls, it’s important to understand how they work. And we’ll do just that in this blog post.

The Basics: Let’s Start With The Good Old Keyboard

Think of a touchscreen as an invisible keyboard placed on your computer monitor. It’s important to understand how a keyboard works so that you can fully comprehend how touchscreens work.


Each key on your keyboard is a switch. When you hit a key, you complete a circuit, allowing current to flow. Different keys produce different currents when pressed, which is how your computer understands the different keypresses.

Let’s take a closer look at how this works:

So on your keyboard, there are two layers of plastic that conducts electricity. In between these two conductors, there is an insulating plastic sheet that has holes. So when you push a key, the two conducting layers touch through the holes. This completes a circuit, generating a current and your computer knows which key you pressed.

Under each key, there is a springy rubber that pushes the key back up to its original position, which breaks the circuit.

Check this out:

What’s amazing about a large touch screen monitor is that it achieves the same exact mechanism as a conventional keyboard, only that it occurs on the surface of the screen. They would block your view if manufacturers used rubber and plastic membranes, so they achieve this invisibly.

The Working Mechanism Behind a Large Touch Screen Monitor

There are a variety of touchscreens and each works in its own special way. For example, some touchscreens are perfectly able to understand multiple keypresses, while others cannot.

The following are the main touchscreen technologies on the market.

Resistive Touchscreens

This is by far the most popular touchscreen technology on the market. It is like a transparent keyboard overlaid on the screen. The upper layer is a flexible electrically conductive polyester. Underneath it is a conductive glass layer. The two are separated by an insulator.

Pressing on the polyester layer forces it down to touch the conductive glass, completing the circuit, which is just the same as your keyboard works. There is a chip inside the device that determines where the touch was and does the required action.

Capacitive Touchscreens

Capacitive touchscreens consist of several glass layers. The inner and outer glass layers are electrical conductors separated by a glass insulator. When you touch the screen, the electrical field changes based on where you touch.

Capacitive touchscreens allow multi-touch. It’s important to note that capacitive screens will not work if touched by plastic pointers, because the plastic is an insulator and will not cause a change in the electrical field.

Infrared Touchscreens

An infrared touchscreen works through an LED grid. It also has cells that detect light on the opposite side of the screen. The LED grid produces light in front of the screen. Touching the screen results in an interruption of one or more beams.

The large touch screen monitor has a microchip which determines where the touch was by identifying the interrupted beams. Since these screens work by interrupting a beam of light, they work just as well whether you use a stylus or your finger.

Surface Acoustic Wave (SAW) Touchscreens

This is one of the more interesting touchscreens as it detects your touch using sound. SAW-based screens use ultrasonic sound, which is too high-pitched for the human ear to hear. These waves are generated at the screen edge and reflected along the screen surface.

A touch on the screen breaks the acoustic waves by absorbing some of the energy. There is a microchip within the device that determines where the touch was and then takes the appropriate action.

Near Field Imaging

If you happen to have an old radio around, you might notice that moving your hand towards it makes it buzz. The reason behind this is that your hand affects the electromagnetic wave on the radio’s antenna.


The closer you move your hand towards the radio, the higher the buzz. This is the mechanism that near field imaging touchscreens use. When your finger gets close to the screen, the electromagnetic field on the screen changes and this is registered as a touch. The chip determines where the touch is and takes the right action.

Why is this important?

If you will use the screen in rough environments like in war or restaurants, this technology is ideal. Also, near field imaging screens can detect touch from styluses, pens, and hands with gloves.

Light Pens

Light pens appeared early in the life of touchscreens. However, their working mechanism is completely different from that of modern touchscreens. Light pens use an electron beam that moves between itself and the monitor continuously.

The pen has a photoelectric cell that detects an electron beam and transmits this to the computer through a cable. This allows the computer to know the exact location of the electron beam and execute the command. In the 1970s, light pens were especially useful in selecting from menus and computer graphics.

Benefits of Touchscreen Displays

Compared to other forms of interactions with computers, touchscreens are very easy to use. The reason is that a touchscreen display can show just the right amount of buttons and information to help one complete a task.

It’s no wonder, touchscreen displays have been a massive success in shop signage, ticket machines at railway stations and voting machines. They are also used in military computers and other areas where physical keyboards would just be too cumbersome.

For smartphones, touchscreens have been a huge success because they show the information required to solve a problem. For example, if you open the phone app, you only see the numbers 1 to 9, and a call button. If you want to type a message, the screen shows a text field and a QWERTY keyboard. In other words, touchscreens change to meet your needs.


Even though touchscreen smartphones and tablets are mainstream, touch-based PCs are still uncommon. Microsoft has voiced its strong belief that touch would be so important in computer interactions, that they would drive mice and keyboards to obsolescence.

However, even though people are comfortable touching and swiping at their phones and tablets, they seem quite content in using mice and keyboards for computer interactions. Whether this changes in the future, we’ll just have to wait and see.


This article shows the different technologies used in a large touch screen monitor. Each technology has its advantages and disadvantages. However, most touchscreen display technologies try to replicate the working of the conventional keyboard, only invisibly.

Ssidisplays has been manufacturing screens for different applications, clients and industries, including the military, corporations, and individuals. Our 15+ years of experience has given us the knowledge and skills to help assess your needs and get the right screen for you. Contact us now to see how we can help you get the ideal screen.