Wireless modem

A wireless modem is used to access the Internet via cell phone operators' networks.

Description

• It is convenient to use in travel and in any situation where there is no access to a Wi-Fi network. It integrates into ATMs, vending machines, security systems, vehicles, remote control systems, etc.;
• Different mobile network rates can be used;
• Easy to install.

USB modem

It is connected to a laptop or tablet via a USB port. It looks like a flash drive.

It only connects one gadget to the Internet.

Standard Networking

Modems can use different standard networks. They differ from each other in the speed of data transmission and the quality of the received connection.

GSM, GPRS, and EDGE

These are the mobile communication standards for 2G. Data rates range from 14 Kbps to 400 Kbps. On your smartphone, this communication standard is indicated by the letter E.

3G

• UMTS – Data transfer rate is 284 Kbps
• HSPA – Data transfer speed is 1.8 Mbps
• HSPA+ – Data transfer speed is up to 42 Mbps

4G (LTE)

4G has a data transfer rate of up to 300 Mbps, while LTE-A has a data transfer rate of up to 1Gbps.

A 4G-supported modem, in case it cannot catch this standard, switches to 3G, since it automatically supports this standard as well.

5G

This is the new generation of the network, which is just getting started. The speeds can reach 20 Gbps.

Router

A router is designed to distribute incoming Internet signals to multiple consumers: computers, laptops, phones, and other gadgets.

Working Principle

The source of the signal for the router is the Internet service provider with whom you, as a consumer, have a contract. The ISP wire is plugged into a special WAN (or Internet) connector on the router.

Furthermore, the router receives the incoming signal from the source and, using a special routing table, distributes it to several consumers. The routing table prescribes and selects the shortest possible addresses to the connected devices. Internet data from the router is only sent to active devices. If you turn off a gadget connected to the router, the router will stop transmitting data to the address corresponding to that device.

Router buttons and connectors

1 - Power on and off button

2 - Connector for connecting the power supply of the device

3 - WAN (or Internet) connector for the network cable (usually blue)

4 - LAN connectors. These are needed to connect your consumers to the router with a network cable (usually yellow)

5 - Reboot button for the router.

Routers can be equipped with a USB connector. It is designed to connect a USB modem with a sim card to the router, which receives the incoming signal.

Interaction with devices

Consumers can connect to the router wired through the LAN ports and the Wi-Fi radio signal.

The router can usually connect from one to four consumers through the wired connection, depending on the number of LAN ports on the router.

The number of gadget connections via Wi-Fi for one router is limited and depends on the router itself and its data transfer rate. If you connect multiple devices via Wi-Fi, the data transfer rate may decrease. In other words, if the input speed of the router is 300 Mbps, and 15 devices are connected to it and working simultaneously, the data transfer rate to devices via Wi-Fi is reduced to 20 Mbps. It is because the router transmits the same rate to the connected devices at the same time. If there are walls, furniture, doors on the way from the router to the connected devices, these obstacles significantly reduce the bandwidth of the routers.

Router settings

Wireless communication protocols

The wireless network works using the 802.11 communication protocol. This protocol has its own varieties: 802.11b and 802.11g. These operate at 2.4 GHz and have limited speeds from 11 Mbps to 54 Mbps. Higher-performance protocols are 802.11ac and 802.11n. They provide higher speeds and 5 GHz frequencies.

Data transfer rate

This is an important parameter on which the performance of the router depends. The data transfer speed is related to the communication protocol.

The 802.11n standard provides speeds of 600 Mbps (at 2.4 GHz and 5 GHz). The 802.11ac standard provides faster speeds than 1300 Mbps at 5 GHz.

Frequency range

Routers can be single-band and dual-band. Its primary frequencies are 2.4 GHz and 5 GHz. The dual-band router supports both of these frequencies because of the two built-in radio modules. The majority of routers operate on the 2.4 GHz frequency. The 5 GHz frequency is preferred by the modern user because it is relatively less crowded.

Number of antennas

The number of antennas in the router allows you to separate data streams and retain a good data rate. Thus, the number of antennas increases the performance of the router.

Built-in firewall

The built-in firewall controls all incoming and outgoing information traffic and protects your home network from spam.

Encryption support

Encryption means the process of encrypting data, which is intended to protect it. An unauthorized user cannot read encrypted data.

Router encryption protocols are WEP, WPA, and WPA2.

Router operating modes

Standard connection

It is supposed that the router is connected via wire, and the Internet signal is distributed via Wi-Fi or wires from the LAN sockets.

WISP mode

It is supposed that the router is connected to the provider through the air rather than by wire, and the Internet signal is distributed via Wi-Fi or by wires from the LAN connectors.

Repeater mode

It is supposed to have two routers. The first receives the signal over the wire from the ISP and distributes the signal. The second router receives the signal from the first router and distributes it to gadgets via Wi-Fi or wires from LAN sockets. This way can be used when it is not possible to run a cable to the second router or when it is necessary to extend the coverage of the Wi-Fi network.

Network Interface Card

This device allows the computer to communicate with the local network and the Internet.

Principle of operation

Once information is received, it is decrypted and transferred to the memory of the network card. Subsequently, the computer processes the received bytes of information.

Network connection

Network connection of the network interface card (NIC) is made via:

• Twisted pair connector

• Optical Connector (SC, ST, MIcz)

There are one or more information LEDs next to the twisted-pair connector, indicating the presence of connection and information transfer.

Speed

Each NIC has a speed limit. So, if your NIC's maximum speed limit is 100 Mbps, but your ISP gives you a fiber-optic speed of 500 Mbps, then your Internet connection speed will not exceed 100 Mbps. In this case, it is recommended that you replace your outdated NIC with a new one. Modern NICs support Internet connection speeds of up to 1 Gbps.

Types

Internal

Internal NICs can be installed in PCI or PCIe slots on the motherboard.

External

Connects to a PC through the USB connector.

Integrated on the motherboard

Network cable connector (1), which interacts with the on-board network card on the motherboard.

Wireless Network Card

If there is no integrated network card, the computer is required to have a network card for wireless data transfer via Wi-fi. Such network cards with an antenna can be connected to the motherboard via a PCI or PCIe connector, and connected to the PC via a USB connector

Projector

A projector is a device designed to render images on a screen and horizontal or vertical surfaces.

Types of projectors for digital images

LCD projector

1 - Projection lamp

2 - Condenser

3 - Lenses

4 - Display

5 - Lens

6 - Luminous flux to the screen

It is constructed like a film projector, only it has a color liquid crystal display inside, instead of film, as in modern displays.

Disadvantages: you can see pixels; the display can burn out due to the bright image.

3LCD projector

1 - Projection lamp

2 - mirrors

3 - LCD monitor

4 - Three channels prism

5 - Display

The system of mirrors divides the luminous flux into three channels (RGB), each of which appears on a different LCD panel. Then the processed light stream is merged into a single image in the three channels prism and displayed on the screen through a lens.

Although the technology is more expensive, this kind of projector no longer shows pixels, and the picture looks saturated.

Compared to an LCD projector, the 3LCD also has a higher noise level because it is necessary to cool three screens instead of one.

LCoS projector

1 - Projection lamp

2 - Mirrors

3 - LCoS panel

4 - Reflecting mirror

5 - Polarizing filters

6 - Prism

LCoS technology may also be called D-ILA, HD-ILA, and SXRD.

It is an improved technology of 3LCD, where a reflective layer has been added behind the liquid crystal layer, so light is reflected and transmitted through the liquid crystal twice upon entering into the display.

The technology has increased the contrast and clarity of the image, but these types of projectors are expensive.

DLP (Digital Light Processing) projector

1 - Projection lamp

2 - Condenser lens

3 - Color wheel

4 - Aspherical lens

5 - DLP chip

6 - lens

7 - Screen

It is called DLP because of the digital light processing. It has one DMD (Digital micromirror device) instead of three LCD screens. The display consists of millions of micromirrors. Each of these mirrors is made of aluminum alloy and can be tilted to one of two positions, differing by 20 degrees. The first position is responsible for white, the second for black. When the position of the mirrors changes rapidly, the pixels on the screen flicker, but the human eye is not able to notice the flicker of the pixels at this speed. The output image is grayed out (because of the rapid change in white and black). However, DLP projectors pass light through a special color wheel to produce a color image.

This disk rotates quickly and paints the pixels one by one.

DLP technology outputs a rich black color on the screen, no grid of pixels is visible, and the mirrors don't burn out because they don't require extensive cooling. That means they are less noisy. Also, these projectors are more compact and portable. However, DLP projectors are less bright than 3LCD projectors.

The older versions of these projectors have a disadvantage: the "rainbow" effect in dynamic and high-contrast scenes. This is related to the rotating color disk. Modern DLP projectors have an increased rotation speed, so the "rainbow" effect disappears.

Moreover, there is a technology of three-matrix DLP projectors that are not inferior to LCD projectors.

Printer

This is a device for printing text or graphic information that is stored in a computer to paper.

Printer Options

Functionality of the device

Printing color

Black and white or color printing.

Printing speed

This indicator shows the number of pages printed per minute.

Printing Cost

This is the cost of replacing the color cartridges in an inkjet printer or replacing the toner roller in a laser or LED printer.

Resolution (dpi)

This indicator shows the print quality of an image or text. The higher it is, the better is the print quality.

For photos good print quality is achieved at a resolution of 2400 dpi, for tables and charts need from 1200 dpi, for text documents 600 dpi is enough.

Photo printing

This is the ability of the printer to print color pictures or photos. For photo printing, the printer must have a color cartridge or cartridges with several shades of different colors. And you also need special paper for photo printing.

Operating system compatibility

This indicator shows its ability to work with various operating systems.

Printer tray layout

The printer tray layout can take up a lot of space. This parameter is relevant for small spaces.

Print format

This parameter indicates the paper size supported by the device. Photo printers support printing in A6 format. For standard printers, the maximum print size is A3; the standard format is A4.

Interface type and wireless connection support

As standard, the printer connects to your computer via USB. It can also be connected to the local network that is used in the office or to Wi-Fi.

Operating principle of printers

Dot-matrix printer

A dot matrix printer creates an image on a sheet of paper using a print head (matrix). This head consists of a set of needles. The set of needles is driven by electromagnets. The head moves along the sheet of paper, and the needles strike it through the ink ribbon.

Matrix printers are no longer used for office or home use. They have slow typing speeds and noisy operations.

Inkjet printer

An inkjet printer works like a dot matrix printer. The image is created from dots, but instead of needle heads, a matrix with liquid dyes (cartridge) is used.

The printing speed of such a printer is 10-30 pages per minute.

Inkjet printers are widespread because of their use in many areas:

• Office - printing A3, A4, A5 sized paper
• Large format printing is used for outdoor advertisement printing
• Interior printers are used for printing posters, stands for interiors
• Photo printers - high-quality print photos

Uninterrupted operation of an inkjet printer is achieved through its regular use. Otherwise, the ink on the print head dries out with prolonged downtime.

Instead of using ink cartridges, inkjet printers can support a continuous ink supply system.

This system delivers ink to the printhead from refillable tanks. The cost of printing is significantly reduced.

Laser printer

The main part of a laser printer is the optical photoconductor drum. It retains an electrical charge on its surface. The laser beam hits the optical photoconductor drum and illuminates individual dots on it. Particles of a special composition (toner) are deposited on the drum and stick only to the charged dots, forming an image. The image is then transferred to the paper under high temperature and pressure.

Laser printers have high print speeds, 80 pages per minute while maintaining high print quality.

LED printer

LED printers use LEDs instead of one laser (laser printer). A different LED is used at each point of the paper print line, so unlike laser technology, the light source remains immovable.

3D printer

This type of printer is designed for printing volume 3D components. They are often used for printing in the medical, industrial, or engineering industries. They are also used for domestic applications such as printing a particular detail. To print a volume 3D figure, you will need a computer program with which you will first need to simulate the model.

Sublimation printers

It is also called a thermal sublimation printer. It can print on a dense surface such as plastic.

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.