What kind of touchscreen displays do modern smartphones have? What is a touchscreen display: how it works - a detailed guide

Today it is no longer possible to surprise anyone with a touchscreen phone. Manual control has become fashionable, but few people think about what happens when you touch the display. I will explain how the most common types of touch screens work. The convenience and productivity of working with digital technology depends primarily on the information input devices used, with the help of which a person controls the equipment and downloads data. The most widespread and universal instrument is the keyboard, which is now ubiquitous. However, it is not always convenient to use it. For example, the dimensions of mobile phones do not allow installing large keys, as a result of which the speed of information input decreases. This problem was solved through the use of touch screens. In just a few years, they have revolutionized the marketplace and have begun to take root in everything from mobile phones and e-books to monitors and printers.

The beginning of the sensory boom

Buying new smartphone, on the body of which there is not a single button or joystick, you hardly think about how you will operate it. From the user's point of view, this is not difficult: just touch the icon on the screen with your finger, which will lead to the performance of an action - opening a window for entering a phone number, SMS or address book. Meanwhile, 20 years ago, such opportunities could only be dreamed of.

The touchscreen was invented in the United States in the second half of the 60s of the last century, but until the early 90s it was mainly used in medical and industrial equipment to replace traditional input devices, the use of which is fraught with difficulties under certain operating conditions. With the decrease in the size of computers and the emergence of PDAs, the question arose about improving their control systems. In 1998, the first handheld with a touch screen and a handwriting input and recognition system appeared Apple Newton MessagePad, and soon communicators with touchscreens.

In 2006, almost all major manufacturers began to release smartphones with touch screens, and after the appearance Apple iPhone In 2007, a real touch boom began - displays of this type appeared in printers, e-books, various types of computers, etc. What happens when you touch the touch screen, and how does the device "know" exactly where you pressed?

How a resistive touchscreen works

Over the 40-year history of the development of touch screens, several types of these input devices have been developed, based on different physical principles that are used to determine the location of a touch. Currently, the most common are two types of displays - resistive and capacitive. In addition, there are screens that can register several clicks at the same time ( Multitouch) or just one.

Screens made by resistive technology consist of two main parts - a flexible top layer and a rigid bottom layer. As the first, various plastic or polyester films can be used, and the second is made of glass. The inner sides of both surfaces are coated with layers of a flexible membrane and a resistive (electrical resistance) material that conducts an electric current. The space between them is filled with a dielectric.

At the edges of each layer, there are thin metal plates - electrodes. In the back layer with resistive material, they are located vertically, and in the front layer - horizontally. In the first case, a constant voltage is applied to them, and an electric current flows from one electrode to the other. This results in a voltage drop proportional to the length of the screen section.

When you touch the touch screen, the front layer flexes and interacts with the back layer, which allows the controller to determine the voltage on it and use it to calculate coordinates touch points horizontally (X-axis). To reduce the influence of the resistance of the front resistive layer, the electrodes located in it are grounded. Then the reverse operation is done: voltage is applied to the electrodes of the front layer, and those located in the back layer are grounded - this is how it is possible to calculate the coordinate of the touching point along the vertical (Y axis). This is how a four-wire (named after the number of electrodes) resistive touchscreen works.

In addition to four-wire, there are also five- and eight-wire touch screens. The latter have a similar operating principle, but a higher positioning accuracy.

The principle of operation and design of five-wire resistive touch screens are slightly different from those described above. The layer of the front resistive coating in them is replaced by a conductive layer and is used exclusively for reading the voltage value on the rear resistive layer. It contains four electrodes at the corners of the screen, the fifth electrode is the output of the front conductive layer. Initially, all four electrodes of the back layer are energized, but on the front layer it is zero. As soon as such a touch screen is touched, the upper and lower layers are connected at a certain point, and the controller detects the change in voltage on the front layer. So he determines that the screen has been touched. Next, the two electrodes in the back layer are grounded, the X coordinate of the touch point is calculated, and then the other two electrodes are grounded, and the Y coordinate of the touch point is calculated.

How Capacitive Touch Screen Works

The principle of operation of capacitive touch screens is based on the ability of the human body to conduct electric current, which indicates the presence of electrical capacity. In the simplest case, such a screen consists of a strong glass substrate on which a layer of resistive material is applied. Four electrodes are placed in its corners. From above, the resistive material is covered with a conductive film.

A small alternating voltage is applied to all four electrodes. At the moment a person touches the screen, an electric charge flows over the skin to the body, and an electric current is generated. Its value is proportional to the distance from the electrode (panel corner) to the point of contact. The controller measures the current at all four electrodes and, based on these values, calculates the coordinates of the point of contact.

The positioning accuracy of capacitive screens is almost the same as that of resistive screens. However, they transmit more light (up to 90%) emitted by the display device. And the absence of elements subject to deformation makes them more reliable: the capacitive screen can withstand more than 200 million clicks at one point and can work at low temperatures (down to -15 ° C). However, the conductive front coating used for positioning is sensitive to moisture, mechanical damage and conductive dirt. Capacitive screens are triggered only when touched with a conductive object (hand without a glove or a special stylus). Screens of this type, made according to the classical technology, are also not able to track several clicks simultaneously.

This capability is provided by the projected capacitive touch screen, which is used in iPhones and similar devices. It has a more complex structure than conventional capacitive screens. On a glass substrate, two layers of electrodes are applied, separated by a dielectric and forming a lattice (the electrodes are located vertically in the lower layer, and horizontally in the upper layer). The grid of electrodes together with the human body forms a capacitor. At the point of touching with a finger, a change in its capacitance occurs, the controller catches this change, determines at which intersection of the electrodes it occurred, and calculates the coordinate of the touch point from this data.

Such screens also have a high transparency and are capable of operating at even lower temperatures (down to -40 ° C). Electrically conductive pollution affects them to a lesser extent, they react to a gloved hand. High sensitivity allows the use of a thick layer of glass (up to 18 mm) to protect such screens.

Working principle of the four-wire resistive touchscreen

1. The upper resistive layer bends and comes into contact with the lower one.
2. The controller detects the voltage at the touch point on the bottom layer and calculates the X coordinate of the touch point.
3. The controller detects the voltage at the touch point on the top layer and determines the Y coordinate of the touch point.

How the 5-wire resistive touchscreen works

1. Touch the screen with any hard object.
2. The top conductive layer flexes and touches the bottom, indicating touching the screen.
3. Two of the four electrodes of the lower layer are grounded, the controller detects the voltage at the point of contact and calculates the coordinate of the point along the X axis.
4. The other two electrodes are grounded, the controller detects the voltage at the touch point and calculates the y-coordinate of the point.

Benefits

• Low cost
• High resistance to dirt
• Can be touched with any hard object

disadvantages

• Low durability (1M clicks at one point for 4-wire, 35M clicks for 5-wire) and vandal resistance
• Low light transmission (no more than 85%)
• Do not support Multitouch

Examples of devices

• Phones (for example, Nokia 5800, НТС Touch Diamond), PDAs, computers (for example, MSI Wind Top AE1900), industrial and medical equipment.

Principle of operation

1. The screen is touched with a conductive object (finger, special stylus).
2. The current flows from the screen to the object.
3. The controller measures the current at the corners of the screen and determines the coordinates of the touch point.

Benefits

• High durability (up to 200 million clicks), the ability to work at low temperatures (down to -15 ° C)

disadvantages

• Susceptible to moisture, conductive contamination
• Do not support Multitouch

Examples of devices

• Phones, touchpads (for example, in the VZO iRiver player), PDAs, ATMs, kiosks.

Principle of operation

1. The screen is touched or brought close to it by a conductive object that forms a capacitor with it.
2. At the point of contact, the electrical capacitance changes.
3. The controller registers the change and determines at which intersection of the electrodes it occurred. Based on this data, the coordinates of the touch point are calculated.

Benefits

• High durability (up to 200 million clicks), the ability to work at low temperatures (down to -40 ° C)
• High vandal resistance (the screen can be covered with a layer of glass up to 18 mm thick)
• High light transmission (more than 90%)
• Support Multitouch

disadvantages

• React to the touch of only a conductive object (finger, special stylus)

Examples of devices

• Phones (for example, iPhones), touchpads, laptop and computer screens (for example, HP TouchSmart tx2), electronic kiosks, ATMs, payment terminals.

Windows 7

Now you can control your computer using the "Scroll", "Forward / Backward", "Rotate" and "Zoom" gestures. The Windows 7 operating system is much better adapted to work with touch displays than all previous versions. 06 this is evidenced by the modified interface and the taskbar, in which square icons appeared in place of rectangular buttons symbolizing running programs - it is much more convenient to press them with your finger. In addition, there is a new feature - Jump Lists, allowing you to quickly find recently opened files or frequently launched items. To activate this feature, just drag the program icon to the Desktop.

For the first time, an option for recognizing touch gestures has been added to the Windows operating system, to which the execution of certain functions is tied. So, in Windows 7, touch scrolling appeared and, like, for example, in the Apple iPhone, the ability to enlarge pictures or documents by moving two fingers in different directions. Not without movement, which is responsible for image rotation. Operations such as copy, delete, and paste can also be assigned separate gestures. The onscreen keyboard buttons are illuminated when touched, making it easy to use on the touchscreen. And with handwriting recognition, you can quickly enter small messages.

In our time, touch screens have long ceased to be exotic. Outwardly they are all similar, but are these displays really the same? Let's look at the design of the main types of sensitive screens, their advantages, disadvantages and scope.

Today, the most widespread sensors are based on capacitive and resistive technologies, as well as on their varieties.

"Multitouch"

This is the name of the technology that allows you to recognize clicks on the touch screen at several points at the same time. This opens up new possibilities in device management. An example of using multitouch technology is the Apple iPhone interface.

Capacitive touch screens

	For example: Tne Prada Phoneby LG

The capacitive touchscreen display actually responds to touch. It is a glass panel coated with a transparent conductive compound. At the corners of the panel there are four electrodes to which an alternating current is supplied. The moment the user touches such a screen with a finger, an electric charge from the conductive layer flows over the skin to the human body. The screen controller measures the current generated across all four electrodes - it is proportional to the distance from the corner of the panel to the touch point. Comparing the obtained values, you can find out the exact coordinates of the point of contact. Sensors operating on this principle can be distinguished "by touch" - they are triggered by a light touch, and respond faster and more clearly to pressing with a fingertip than with a nail. Moreover, they do not react to pressing any other objects, especially if they are non-conductive. Therefore, a phone with such a screen cannot be operated with a gloved hand. In addition, as the temperature decreases, the electrical characteristics of the sensor change, and the screen begins to work worse. We add that this principle is usually used in notebook touchpads.

	For example: Apple iPhone

Projected capacitive screens

There is another type of capacitive sensor - a projected capacitive screen. On the back there is a grid of electrodes. At the point where the hand touches, the electrical capacitance changes (according to the laws of electrodynamics, the human body is a capacitor), the controller determines at which intersection of the electrodes this happened, and calculates the coordinates. Such screens, in addition to high transparency and durability, have two more important advantages - the glass-substrate can be made arbitrarily strong (and rather thick), moreover, they support "multitouch". The downside is lower accuracy compared to conventional capacitive technology.

Resistive touch screens

	For example: HTC Touch Diamond

The resistive sensor is de facto pressure sensitive. The screen consists of two plates, between which there is a non-conductive compound. If you touch the outer flexible (and transparent) plate with your finger (or any other object - in this case it does not matter), the plates are closed and current begins to flow at the point of contact. To determine the location of the touch, the screen controller measures the voltage between the electrodes located at the edges of the panel in pairs. Such a screen is called 4-wire (there are also 5-wires, with some differences).

The peculiarity of the resistive screen is that it requires physical effort to trigger it, and it recognizes pressing with a fingernail better than a pad, reacts to any objects touching the surface. Devices with resistive screens are often equipped with styluses. Such a display provides a higher control accuracy (with a stylus it is possible to literally hit a pixel, while a finger on a capacitive screen can only hit a large enough area), but due to constant contact with hard objects, the flexible plate is quickly covered with scratches. Most mobile devices are equipped with resistive screens.

Other types of touch screens

There are also a number of sensor technologies, often quite exotic. For example, using a grid of infrared rays or even generating ultrasonic vibrations. The latter is known as surface acoustic wave technology. There are systems based on cameras that track motion ("multitouch" is also supported here), and on the basis of strain-gauge coatings, the deformation of which changes the electrical resistance.

Everyone has probably heard about the development of tactile displays by companies, and this is no longer a myth. The only obstacle on the way to a wide audience is the emergence of a universal screen with the highest sensitivity, that is, today specialists are faced with the task of making a tactile display, in all respects, practical. Such an alternative to vibration motors will help to recreate contact with the device, as with a push-button device, and even more ...

Touchscreen displays of the near future

Thanks to some companies, the progress of technology is evident, and now there are not one, but several prototypes. One of these was Microsoft, its research group "" under the leadership of Hong Tan, was able to move in the tactile direction.

A group of specialists have spent several years creating a feedback screen, and their work is already presented in several variations, including those based on Nokia Lumia. You can verify the state of affairs from the video clip below:

According to lead researcher Hong Tan, touchscreens need to evolve into something more. “What can be considered a really cool achievement is to take a smooth piece of glass and make it something special,” says Ms. Tang. "It's almost magic."

Researchers at Microsoft work in two directions, developing the hardware and software components of the technology. The main task is full feedback, not only on pressing the number buttons, but also on the image as a whole. This is how some of the screen options give you a real feel for textures under your fingers. One example is the chessboard from the Nokia Lumia app. Different colored cells have different tactile effects.

Instead of an afterword

Basically, the technology of future screens is based on stimulating receptors on the skin, as well as muscle motility. On the screens you can feel not only the punching of the surface under the finger, but also a characteristic click, indicating contact.
“When you type on the virtual keyboard of your smartphone, the outer layer literally instantly flexes under your fingers. This is a very slight deflection, but it is also enough for your fingers to receive a signal that reminds you that you have pressed a button, ”says Ms. Hong.

Application

Touch screens are used in payment terminals, information kiosks, trade automation equipment, PDAs, mobile phones, game consoles, operator panels in industry.

Pros and cons of handheld devices

Advantages

• Simplicity of the interface.
• The device can combine small size and large screen.
• Speed \u200b\u200bdial in a relaxed environment.
• The multimedia capabilities of the device are significantly expanded.

disadvantages

Advantages and disadvantages in stationary devices

Advantages

In information and vending machines, operator panels and other devices in which there is no active input, touch screens have established themselves as a very convenient way of human-machine interaction. Advantages:

• Increased reliability.
• Resistance to harsh external influences (including vandalism), dust and moisture resistance.

disadvantages

These disadvantages prevent the use of only touch screen in devices with which a person works for hours. However, in a well-designed device, the touch screen may not be the only input device - for example, at the cashier's workplace, the touch screen can be used to quickly select an item, and the keyboard can be used to enter numbers.

How touchscreens work

There are many different types of touchscreens that work on different physical principles.

Resistive touch screens

Four-wire shield

How the 4-wire resistive touchscreen works

The resistive touchscreen consists of a glass panel and a flexible plastic membrane. Both the panel and the membrane are coated with a resistive coating. The space between the glass and the membrane is filled with micro-insulators, which are evenly distributed over the active area of \u200b\u200bthe screen and reliably insulate conductive surfaces. When the screen is pressed, the panel and membrane are closed, and the controller, using an analog-to-digital converter, registers the change in resistance and converts it into touch coordinates (X and Y). In general terms, the reading algorithm is as follows:

1. A voltage of + 5V is applied to the upper electrode, the lower one is grounded. The left and right are short-circuited, and the voltage across them is checked. This voltage corresponds to the Y-coordinate of the screen.
2. Similarly, + 5V and "ground" are supplied to the left and right electrodes, the X-coordinate is read from the top and bottom.

There are also eight-wire touchscreens. They improve tracking accuracy, but do not increase reliability.

Five-wire shield

The 5-wire shield is more reliable due to the fact that the resistive coating on the membrane is replaced by a conductive one (the 5-wire shield continues to work even with a cut membrane). The rear window has a resistive coating with four electrodes at the corners.

Initially, all four electrodes are grounded, and the membrane is "pulled up" by a resistor to + 5V. The diaphragm voltage level is constantly monitored by an analog-to-digital converter. When nothing touches the touch screen, the voltage is 5 V.

As soon as the screen is pressed, the microprocessor senses the change in membrane voltage and begins to calculate the coordinates of the touch as follows:

1. The two right electrodes are supplied with a voltage of + 5V, the left ones are grounded. The voltage on the screen corresponds to the X-coordinate.
2. The Y-coordinate is read by connecting both top electrodes to + 5V and both bottom electrodes to ground.

Features:

Resistive touchscreens are cheap and resistant to dirt. Resistive screens react to touch with any smooth solid object: hand (bare or gloved), pen, credit card, pick. They are used wherever vandalism and low temperatures are not excluded: for the automation of industrial processes, in medicine, in the service sector (POS terminals), in personal electronics (PDA). The best samples are accurate at 4096 x 4096 pixels.

The disadvantages of resistive screens are low light transmittance (no more than 85% for 5-wire models and even lower for 4-wire ones), low durability (no more than 35 million clicks per point) and insufficient vandal resistance (the film is easy to cut).

Matrix touch screens

Design and working principle

The design is similar to the resistive one, but simplified to the limit. Horizontal conductors are applied to the glass, and vertical conductors are applied to the membrane.

When you touch the screen, the conductors touch. The controller determines which conductors are closed and transmits the corresponding coordinates to the microprocessor.

Features:

They have very low accuracy. The interface elements have to be specially arranged taking into account the cells of the matrix screen. The only advantage is simplicity, low cost and unpretentiousness. Typically, matrix screens are polled row by row (similar to a matrix of buttons); this allows you to establish multitouch. They are gradually replaced by resistive ones.

Capacitive touch screens

Design and working principle

A capacitive (or surface-capacitive) screen takes advantage of the fact that a large object conducts alternating current.

A capacitive touchscreen is a glass panel covered with a transparent resistive material (usually an indium oxide / tin oxide alloy). The electrodes located at the corners of the screen apply a small alternating voltage to the conductive layer (the same for all corners). When you touch the screen with a finger or other conductive object, current leakage occurs. In this case, the closer the finger is to the electrode, the lower the resistance of the screen, which means that the current is greater. The current in all four corners is recorded by the sensors and transmitted to the controller, which calculates the coordinates of the touch point.

Earlier models of capacitive screens used direct current - this simplified the design, but with poor user contact with the ground, it led to malfunctions.

Capacitive touch screens are reliable, about 200 million clicks (about 6 and a half years of clicks with an interval of one second), do not let liquids through and perfectly tolerate non-conductive pollution. Transparency at 90%. However, the conductive coating directly on the outer surface is still vulnerable. Therefore, capacitive screens are widely used in machines only installed in a weather-protected room. Does not respond to gloved hands.

It should be noted that due to differences in terminology, surface and projection capacitive screens are often confused. According to the classification used in this article, the screen, for example, iPhone is projection-capacitive, but not capacitive.

Projected capacitive touch screens

Design and working principle

A grid of electrodes is applied to the inside of the screen. The electrode together with the human body forms a capacitor; electronics measure the capacity of this capacitor (gives a current pulse and measures voltage).

Features:

The transparency of such screens is up to 90%, the temperature range is extremely wide. Very durable (bottleneck - complex electronics that handle pressing). Glass with a thickness of up to 18 mm can be used on PёSE, which leads to extreme vandal resistance. They do not react to non-conductive pollution, conductive ones are easily suppressed by software methods. Therefore, projected capacitive touch screens are widely used both in personal electronics and in automatic machines, including those installed on the street.

It should be noted that due to differences in terminology, surface and projected capacitive screens are often confused. According to the classification used in this article, the iPhone screen (the founder of the technology boom, circa 2007) is projected capacitive.

Touchscreens on surface acoustic waves

Design and working principle

The screen is a glass panel with piezoelectric transducers (PEP) located in the corners. There are reflective and receiving sensors at the edges of the panel. The principle of operation of such a screen is as follows. A special controller generates a high-frequency electrical signal and sends it to the probe. The probe converts this signal into a SAW, and the reflective sensors reflect it accordingly. These reflected waves are received by appropriate sensors and sent to the probe. The probe, in turn, receives the reflected waves and converts them into an electrical signal, which is then analyzed by the controller. When you touch the screen with your finger, some of the acoustic energy is absorbed. The receivers record this change, and the microcontroller calculates the position of the touch point. Reacts when touched by an object capable of absorbing a wave (finger, gloved hand, foam rubber).

Features:

The main dignity screen on surface acoustic waves (SAW) is the ability to track not only the coordinates of the point, but also the force of pressing (here, rather, the ability to accurately determine the radius or area of \u200b\u200bpressing), due to the fact that the degree of absorption of acoustic waves depends on the pressure at the point of contact the screen does not bend under finger pressure and does not deform, therefore, the pressing force does not entail qualitative changes in the processing of the data on the coordinates of the impact by the controller, which records only the area that blocks the path of acoustic impulses). This device has a very high transparency as the light from the imaging device passes through glass that does not contain resistive or conductive coatings. In some cases, glass is not used at all to combat glare, and the emitters, receivers and reflectors are attached directly to the display device screen. Despite the complexity of the design, these screens are quite durable. According to the statement, for example, of the American company Tyco Electronics and the Taiwanese company GeneralTouch, they can withstand up to 50 million touches at one point, which exceeds the resource of a 5-wire resistive screen. Surfactant screens are mainly used in slot machines, in guarded information systems and educational institutions. As a rule, surfactant screens are distinguished into ordinary - 3 mm thick, and vandal-resistant - 6 mm. The latter can withstand a punch from the average man or a 0.5 kg metal ball falling from a height of 1.3 meters (according to Elo Touch Systems). The market offers options for connecting to a computer both via the RS232 interface and via the USB interface. At the moment, the most popular are controllers for SAW touch screens that support both types of connection - combo (data from Elo Touch Systems).

The main disadvantage the screen on the SAW are malfunctions in the presence of vibration or when exposed to acoustic noise, as well as when the screen is dirty. Any foreign object placed on the screen (for example, chewing gum) completely blocks its operation. In addition, this technology requires touching with an object that necessarily absorbs acoustic waves - that is, for example, a plastic bank card is not applicable in this case.

The accuracy of these screens is higher than matrix screens, but lower than traditional capacitive screens. They are generally not used for drawing and typing.

Infrared touch screens

The principle of operation of the infrared touch panel is simple - the grid formed by horizontal and vertical infrared rays is interrupted when you touch the monitor with any object. The controller determines the location at which the beam was interrupted.

Features:

Infrared touch screens are afraid of contamination and therefore are used where image quality is important, such as e-books. Due to its simplicity and maintainability, the scheme is popular with the military. Intercom keyboards are often made on this principle. This type of screen is used in Neonode mobile phones.

Optical touch screens

The glass panel is equipped with infrared illumination. At the “glass-air” border, a complete internal reflection is obtained, at the “glass-foreign object” border, light is scattered. It remains to capture the scattering pattern, for this there are two technologies:

Features:

They allow you to distinguish between pressing with your hand and pressing any objects, there is a multitouch. Large touch surfaces are possible, right up to the chalkboard.

Strain gauge touch screens

React to screen deformation. The accuracy of the strain gauge screens is low, but they can withstand vandalism perfectly. The application is similar to capacitive projection: ATMs, ticket machines and other devices located on the street.

DST touch screens

Main article: Dispersive Signal Technology

The DST (Dispersiv'e Signal Technology) touch screen reacts to glass deformation. It is possible to press the screen with your hand or any object. A distinctive feature is a high reaction speed and the ability to work in conditions of severe screen pollution.

Induction touch screens

An induction touchscreen is a graphics tablet with an integrated display. These screens only respond to a special pen.

They are used when it is required to respond specifically to pressing with a pen (and not with a hand): high-end art tablets, some models of tablet PCs.

Pivot table

1 Supported with limitations.
2 If only a glass panel is needed, without any transparent conductive films - conventionally 95%. If you don't even need it (you can apply the standard screen coverage) - conditionally 100%
3 High - to the pixel (accurately tracks a sharp pen). Medium - up to several pixels (sufficient for finger clicks). Low - in large blocks of the screen (drawing is impossible, very large interface elements are required).
4 Limited by electronics reliability
5 Limited by contamination of the sensor
6 Ogran - limited access equipment (personal electronics, industrial equipment). Premises - general access in a protected area. Street - Shared on the street.
7 Software emulation, handles a maximum of 2 clicks.

see also

• Touchphone

In the movie Die Hard, Bruce Willis's character takes a close look at a technical novelty of the time - the visitor touchpad at Nakatomi Plaza.

Links

• Replacing the touchscreen Instructions for replacing the touchscreen

Notes

1. Touch Screen - History of the Touch Screen Computer Interface (eng.)
2. Company history from Elographics to Elo TouchSystems, 1971 - present - Elo TouchSystems - Tyco Electronics
3. HP History: 1980s
4. In resistive screens, there is a recoil when pressed - this makes working with your hands more comfortable. Besides, in some phones a successful press is confirmed by vibration. But such feedback, of course, is not enough to distinguish one interface element from another by touch.
5. Mukhin I.A.