Sound speakers and headphones

Sound (acoustic) speakers and headphones are devices for transmitting sound.

The computer has no sound output systems, so it requires audio speakers or headphones for sound reproduction.

Operating principle

Sound devices have a loudspeaker inside. The speaker is designed to convert electrical vibrations into sound vibrations that the human ear can hear.

Inside the speaker, there is a special coil with a conductor wound on it. An electric current is applied to the contacts of this coil. The frequency of the alternating current changes with the same frequency of oscillation as the music being played. By changing this frequency, the poles of the coil are reversed. The reversal of the poles makes the coil oscillate. The oscillation of the coil's magnetic poles is transmitted to the diaphragm, which pushes air in front of it, creating sound vibrations (waves).

Built-in amplifier

The amplifier in the audio device allows you to adjust the strength of the signal in the speaker. This increases the quality of the sound signal playback.

Power

Power is the main characteristic of audio hardware. It determines the volume of the audio system. For music in the background in the workplace, a speaker with 5 watts is sufficient. To use the speakers in a small room area, a power of 5 to 20 watts is required. For sound speakers used outdoors or in a large hall, the speaker's necessary power is 50 watts or more.

Audio formats

Mono-channel sound

Monaural audio uses a single channel. This channel can be played on multiple audio devices, but all devices will play one signal copy.

Stereo sound

The stereo audio uses two channels. One channel sends sound to the left speaker, the other channel sends sound to the right speaker. By controlling these signals, you can control the position of the sound. The user will hear sounds coming from different modes.

Multichannel (surround) sound

Multichannel (surround) sound

In multichannel audio playback, more than two channels are used. A specific sound mode has its own dedicated channel with a separate audio speaker.

Connection

3.5mm connector

Computers and laptops are equipped with special 3.5-mm sound card connectors, through which sound equipment is connected.

To determine which port the plug goes to, board manufacturers usually mark the connector with a color: green for headphones or speakers, pink for the microphone.

Most modern laptops and computers are equipped with a single connector that can simultaneously detect an input sound device and a microphone.

The sound quality of wired audio devices over a 3.5mm cable depends on the quality of the sound card or amplifier to which it is connected.

USB connector

The advantage of a USB audio device over a 3.5 mm connector is consistent sound quality. When using USB, the computer sends the signal in digital form; the sound device processes it internally, converts it into an analog format and plays it back.

Wireless connection

Modern models of audio devices allow the user to connect the device remotely. This is done through a Bluetooth connection.

Monitor

It is a device for presenting information in a visual form.

Parameters

• Brightness – is a maximum level of white color on the screen.
• Contrast – is the ratio of brightness of the lightest shade to the darkest shade that the monitor can display simultaneously.
• The aspect ratio of the monitor screen - is standard (4:3), widescreen (16:9, 16:10), or another ratio (e.g., 5:4).
• The size of the monitor is usually given by the diagonal size in inches.

Resolution – is the number of pixels horizontally and vertically. The higher the display's resolution is, the better is the image quality.

• 720 pixels horizontally and 480 vertically;
• HD - 1280 pixels horizontally and 720 vertically;
• Full HD - 1920 pixels horizontally and 1080 vertically;
• Ultra HD - 3840 pixels horizontally and 2160 vertically;
• 4K - 4096 pixels horizontally and 2160 vertically;
• 8K UHD - 7860 pixels horizontally and 4320 vertically.
• The screen refresh rate (Hz) is the display's refresh rate. The time between refreshes is measured in milliseconds (ms), and the display refresh rate is measured in Hertz (Hz). A high refresh rate ensures a smoother image and a higher FPS.
• Viewing angle – is the angle from which the viewer can distinguish a clear image on the screen.

Types of monitors by screen type

Cathode ray tube (CRT)

It is a monitor based on a cathode ray tube. The first available monitors came from this technology.

Monitors and televisions that have been made with this technology are harmful to the eyesight as the eyes are overworked and always under strain.

Liquid Crystal Display (LCD)

It is a liquid crystal screen. The main component of this monitor is an LCD (Liquid Crystal Display) matrix.  

A matrix consisting of several plates is used to receive and display the picture on the screen. The backlight is also used, which is a fluorescent lamp with a cold cathode.

LED monitor

It is a monitor whose pixels are one or more semiconductor diodes.

The difference between LCD and LED monitors is the backlighting. LED monitors use light-emitting diodes to provide an equal distribution of light rays. This affects the depth of reproduction and the high level of contrast.

OLED monitor

These are organic light-emitting diodes (OLED) monitors.

Light in an OLED monitor is emitted by each pixel individually. A bright white or colorful colored pixel can sit next to a black or completely different colored pixel, and they will not affect each other.

OLED monitors are thinner and lighter than LCD or LED-backlit monitors. OLEDs also have a much wider viewing angle and a much shorter refresh time.  

QLED monitor

In QLED, each pixel emits its own light using quantum dots - tiny fragments of semiconductors only a few nanometers in size. Quantum dots can produce bright, vivid, and varied colors, surpassing OLED in this respect. However, QLED technology requires additional backlighting for high-quality images. And the need for additional backlighting means that QLED panels cannot be as ultra-thin as OLED.

Types of monitor interface cables

1. RCA type composite connector

These connectors are used in video and audio equipment. They are cylindrical in shape. The signal contact is positioned in the center. There is a ground contact in the form of a cylinder that covers the signal contact.  

Yellow is for video transmission only.

Red connector is used to transmit two-channel audio signal in stereo mode in relation to the right channel.  

The white connector is used for the monaural signal. It can also be used for the left-hand channel of a stereo two-channel audio signal. 

2. Component

A component cable splits the video signal transmission into 3 components (3 cables) and is used for separate transmission of luminance and color signals.

3. S-Video

This connector provides higher transmission of brightness, color, and image quality than composite standards

4. VGA (D-Sub)

VGA (D-Sub) is an analog fifteen-pin connector. It is used to connect a computer or laptop to a monitor.

5. DVI

This is a digital video interface. It is designed to transmit video images to digital devices (monitor, TV, projector).

6. USB

USB 2.0 and newer connectors allow the connection of video devices.

7. HDMI

This interface enables high-resolution, high-definition digital video data to be transmitted.

8. DisplayPort

This is the interface standard for digital monitors. Version 1.4 is a more modern interface for connecting audio and video equipment. The difference to HDMI is a wider channel for data transfer.

9. Thunderbolt

This hardware interface connects peripheral devices to the computer at a maximum data transfer rate.

Image scanner

It is a device that reads an item (image, text) and creates a digital copy of it.

Operating principle

Scanning with an analog-to-digital converter creates a digital description of the image. The final result of the scanner is a file that can be opened on a computer, phone, or tablet).

Stages of scanner operation

• Place a sheet of paper on the side you want to scan on the scanner's work surface
• Select the settings (resolution, color, file format, etc.)
• Scanning is initiated by a button on the scanner or by a command from a device connected to the scanner
• When the scanning signal is received, the mechanisms that move the lamp across the entire area are activated
• The lamp shines on the data carrier, reflecting the information on the mirror system. This system allows the data to enter the analog-to-digital converter
• The received information is sent to a computer

Types

Flatbed Scanner

This type of scanner is used at homes and offices. It is called a flatbed scanner because a sheet of paper is placed on a flat surface - the scanner glass. Many types of data carriers can be scanned with this scanner, from an A4 sheet of paper to thick books.

Pulling Scanner

This type of scanner pulls a sheet of paper through its internal components. It only scans separate sheets of paper.

Manual Scanner

This type of scanner is professional equipment used for work in offices and enterprises. It allows large quantities of information to be scanned quickly.

Industrial

This scanner allows you to digitize an entire book yourself.

Streaming Scanner

This type of scanner is professional equipment used for work in offices and enterprises. It allows large quantities of information to be scanned quickly.

Drum Scanner

This scanner distinguishes between light and dark colors more clearly, whereas flatbed scanners take them for black and white. This results in high color sensitivity in terms of shades of light and dark tones. It is used in the printing industry.

Microphone

It is a device that converts acoustic vibrations into electrical signals.

Various types of microphones are used to record sound. The most sophisticated ones use microchips and additional power supplies.

Dynamic microphone

The simplest microphone is based on the principle of an eardrum. The diaphragm moves the induction coil. This movement creates electrical pulses in the coil. The pulses are sent through wires to the sound recorder.

Dynamic microphone

1 – Sound waves

2 – Diaphragm

3 – Output signal

4 – Permanent magnet

5 – Induction coil

These microphones are used for performing on stage or recording vocals. They have lower sensitivity and volume but can manage high acoustic pressure.

Condenser microphone

1 – Sound waves

2 – Membrane and electrode

3 – Signal

4 – Resistance

5 – Capacitor

This microphone amplifies sound using a thin diaphragm made of conductive material. The membrane is positioned parallel to the metal plate, with which it forms a capacitor coil.

As the membrane vibrates, the capacitance of the condenser changes, generating electrical pulses that are transmitted to the sound recorder.

These microphones are highly sensitive and capture ambient sounds perfectly. They are used in recording studios.

Computer microphone

For conversations or recording podcasts

For regular conversations, any budget microphone is suitable. For business conversations at work, a unidirectional condenser microphone is suitable. This microphone allows the user to retain the vocal dynamics and natural sound.

For this purpose, a pop-filter, which stops strong gusts of air when making loud sounds, is useful.

For computer games

For gaming, headphones with a condenser microphone and noise-canceling function are ideal.

Webcam

A webcam is a digital video and photo camera connected to a computer. It is used to transmit images over the Internet.

You can purchase webcams separately, but they are already built into laptops and smartphones.

The camera connects to a computer and delivers images to a web server by request, either continuously or at intervals. Some cameras with special software work independently as a web server and send images via e-mail.

Security webcams can be equipped with motion detectors, external sensors, night vision sensors, etc.

Device

The main part of a webcam is the sensor. It is a semiconductor chip that consists of millions of light-sensitive squares. These squares are called pixels.

The camera also has an analog-to-digital converter and a microprocessor.

How it works

1 - Lens

2 - Optical filter

3 - Sensor

4 - analog-to-digital converter

5 - Compression block

6 - Central processor

7 - Flash memory

8 - RAM

9 - Internet

10 - COM port

11 - Input/output unit

1. The light sensor in the cameras is used to capture the light image and transmit it to the microprocessor. This sensor converts the captured light into electrical signals.
2. The central microprocessor transmits the signal to the analog-to-digital converter. It converts the analog image into a digital one, in other words, into a code of zeros and ones.
3. The compression units compress the digital signal into MPEG format files.
4. The information is transmitted to a computer via a USB interface, then to the Internet.

Main parameters

Resolution

It means the number of pixels vertically and horizontally on the image sensor. The more pixels, the higher the image quality is.

FPS

This is the number (or frequency) of frames per second that the camera can process. Budget cameras have frames per second of about 24. A good fps rate is between 50 and 60 frames per second.

Computer Mouse

A computer mouse is an input device for entering information into a computer. Computer mice, like keyboards, are available as wired and wireless. 

A wired and wireless mouse adapter plugs into the USB port.

PS/2 port, which connects the mouse and keyboard, is obsolete. It is rarely found in modern computers.

Principle of operation

The device tracks its movement on the working surface with a movement sensor and transmits the movement information to the computer's operating system. The operating system makes the cursor move. The keys on the mouse drive a context menu, activate a specified feature, or scroll through web pages.

Keys

1 – The right button. It reveals a context (additional) menu that provides additional actions.

2 - Scroll Wheel. It allows you to scroll up or down files of different formats.

3 - The left button. It is used to open documents and launch programs.

4 and 5 - Auxiliary buttons. The mouse may have auxiliary (side) buttons for convenient work and games.

Types

Optical Laser Mouse

This mouse uses a type of optical sensor that applies a semiconductor laser. The laser emits light in the infrared range. The sensor in the mouse picks up the wavelength of the reflected light, which varies depending on the surface.

Optical LED Mouse

This mouse has an optical sensor (camera) with a small resolution sensor. It contains a light source (LED) and two lenses. The LED is structurally mounted at an angle to the working surface. A CMOS sensor receives the reflected beam. According to the comparison of different consecutive pictures by the sensor, it is concluded about the movement of the mouse. Based on these signals, the processor realizes in which direction to move the cursor on the monitor screen.

Gyroscopic Mouse

These mice include a gyroscope that detects movement on the mouse pad and in space.

Induction mouse

These mice use a special pad that operates on the principle of a graphics tablet. The mouse emits electromagnetic waves and the mousepad acts as a receiver. This is how the mouse interacts with the mat.

Computer keyboard

A computer keyboard is a device that allows the user to enter data into a computer. It consists of a set of keys arranged in a specific order. The keyboard is available as a wired or wireless keyboard.

A wired keyboard and a wireless keyboard adapter plug into a USB port.

PS/2 port, which connects the mouse and keyboard, is obsolete. It is rarely found in modern computers.

Typing keys

1 – Control keys. They are used to perform certain actions. They can be used alone or in combination with other keys.

2 – Function keys. These keys execute a specific action on the system. For example, on a notebook, the combination of the «Fn» key and one of the function keys (F1, F2, F3, etc.) increase or decrease the sound, brightness, and so on.

3 – Indicators for enabling Caps Lock, Scroll lock, Num lock.

4 – Keys to work with reading and documents. These include keys: Page Up, Page Down, Home, End, Del, Esc.

5 – Auxiliary keys, enabled by pressing Num lock.

6 – Cursor control keys.

7 – Alphanumeric keys for typing text, numbers, symbols.

Types of keyboards

Membrane keyboards

 membrane keyboard consists of an elastic silicone membrane that squeezes out when the key is pressed.

Pressing the key bridges the contact lines on the printed circuit board.

This is a budget type of keyboard. Eventually, the silicone membrane becomes worn out, and the printed circuit board cannot read the keypress signal.

Mechanical keyboards

Under each mechanical key, you find a separate switch system. Using switches makes the keyboard more reliable. In addition, the keyboard has a characteristic "click" when the key is pressed. This type of keyboard ranks in the more expensive segment than membrane keyboards.

Hybrid keyboards

These keyboards are a combination of mechanical and membrane keyboards. The combination of these types of keyboards provides the membrane keys with tighter feedback and longer life.

Touch keyboards

The touch keyboard is a full-fledged display with a high-precision array that senses every press of the fingers.

Flexible keyboards

Flexible keyboards are available with different numbers of keys. There are also models in different colors, matte and glossy. In addition, this keyboard is sealed and resistant to moisture and dust.

Optical keyboards

The optical keyboard features mechanical moving elements. Once the key is pressed, its rod moves downward and returns back up by spring action. There is an emitter inside the key, which directs an infrared beam to a special sensor.  The rod of the key overlaps the beam, but when pressed, it allows it to connect to the sensor, sending a command to the system.

RGB backlight

RGB backlight allows you to change the color of certain keys and the keyboard as a whole. This can be useful when playing computer games as well as when working.