The phone has changed a lot since its invention. Today, this is not even the device that simply transmits the voice of one person to another over long distances. In the modern world, this is a complex technical tool with artificial intelligence that can not only make calls and send messages, but also play video and audio, access the Internet, process large amounts of information, and simultaneously perform many operations and tasks. What do we know about how the phone works and how it works? In the framework of this article, we will try to understand this issue.
The birth and evolution of the telephone
The founder of the first apparatus for transmitting information over a distance is considered to be Samuel Morse, who invented the telegraph and Morse code.
It is difficult to call this device a full-fledged phone, since information was transmitted using contact closure and speciallyMorse code, as it is often called for short, developed for it.
Some historians attribute the invention of the first telephone to Antonio Meucci, which he called the telephotophone. He developed the drawings, but for some unknown reason did not register his creation. Therefore, the patent belongs to Alexander Bell. His device was without a call and outwardly had nothing to do with modern devices.
The telephone device was bulky and inconvenient for negotiations, weighing about eight kilograms. However, this did not prevent its popularization and wide distribution in all countries. By the beginning of the twentieth century, there were already more than ten thousand stations in the world. Each time, changes and improvements were made to its design, so a separate microphone and speaker appeared in its design.
The global construction of automatic telephone exchanges has led to the modernization of devices. They got a handset and a disk for dialing the subscriber's number. The dial contained numbers and letters, except for the letter "З", as it resembles a three. On push-button fixed phones, this numbering has been preserved to this day. This is not done at all to send messages, it's easier to remember the number. The first devices in Soviet Russia belonged to two companies: Ericsson and Siemens. These were phones without a charger, operating on the principle of transmitting and receiving simple electrical impulses.
Cordless phones appeared in our country in the 70s of the twentiethcentury. They transmitted a radio signal to the base, which, in turn, communicated with another subscriber along the line through switches. Their trade name is "Altai", they were a prototype of mobile communications. Such an installation weighed seven kilograms. It was not suitable for carrying, so it was equipped with vehicles of operational services. Ceased to exist only in 2011.
In Russia, the first cellular communication appeared in 1991, and it worked according to the NMT standard. The first suppliers of mobile phones were Nokia and Motorola. The prices for the devices were cosmic, and only very rich people could afford them. The GSM standard appeared in 1993 and, having defeated its competitors, took root in many countries. It allows you to implement a lot of functionality, including sending short messages. Initially, they were supposed to be sent as service notifications, but users liked the option so much that it turned into a separate service of mobile operators.
With the advent of the era of portable devices, the device of mobile phones became more and more complex, the size and weight - less, and the possibilities - more. From three-kilogram giants, they have become miniature communications equipment that can easily fit even in the hand of a child. Over time, the real push-button keyboard was replaced by a virtual one on the touch screen. Cameras, fingerprint scanners and many other devices appeared on the panel.
How analog phones work
Rotary and touch dial telephone device similar in availabilitycomposite blocks, but differs in the principle of operation. Units include the following modules:
- Handset with microphone and speaker.
- Phone.
- Caller.
- Dialing unit.
- Transformer.
- Lever switch.
- Separating capacitor.
- RF module (portable stations).
The lever switch is responsible for connecting the device to the subscriber line. In the cordless telephone device, the connection is conditional on the handset being powered on.
Microphone converts sound waves into electrical signals. Devices are divided into electrodynamic, capacitor, coal, electromagnetic and piezoelectric. They are also divided into active and passive. Active ones form an electromagnetic impulse from sound, passive ones change the parameters of other nodes, mainly capacitance and resistance. The latter require an additional power supply.
The phone translates electrical impulses into sound. The electric current flowing through the coils forms an alternating magnetic field, which causes the speaker membrane to vibrate. Electrodynamic and electromagnetic devices use a differential magnetic system, piezoelectric devices deform the elements of the membrane of sound frequency sources associated with it.
The calling unit can be induction and electronic. Required to notify the subscriber of an incoming call. The first, with the help of the current flowing in the coils, makes the striker vibrate and hit the ringing cups. The electronic unit processesinformation about the incoming signal and redirects it to a common speaker in the form of pulses of a given frequency, which is called a ringtone.
The RF module is only present in the cordless phone unit. It is designed to exchange information between the phone and the receiver via radio signals.
The transformer connects the individual speaking nodes to each other. Also eliminates the effect of local echo in the handset and is responsible for matching with the line impedance.
A decoupling capacitor is needed to connect the phone to the line in the mode of receiving an incoming signal and waiting for an outgoing one. Supports high resistance to large input voltage and low resistance to small input voltage.
The dialer is pulse (disk) and electronic (button). In the first variant, the mechanical wheel, rotating, closes the contacts and sends signals to the PBX. Their number corresponds to a specific number of the subscriber's number. Electronic ones work through integrated circuits that artificially generate pulses using solid-state relays and send them to the station's receiver. Modern PBXs still retain this method of calling a subscriber, but more often use tone dialing. Modern devices also support IP-telephony. The principle of operation of tone dialing is to generate short-term signals of preset frequencies, each value of which corresponds to a certain number of the number. The device for connecting a telephone via IP protocol involves the use of a provider's server via a dedicated Internet channel from which a call is made. Mobile devices send radio signals of a given frequency to the communication system of cell towers.
The principle of operation of devices in wired networks
In order to fully understand the mobile phone, you need to know how the analog PBX system works. Although cell phones are complex digital structures with integrated circuits, they operate on the basic principle of conventional fixed phones.
Each service provider assigns unique identification numbers to its customers by which it distinguishes them from one another. In this case, this is called the number of the subscriber or connection point to which the wires fit. When the PBX sends a signal, the phone is in the off state, that is, the handset is on the machine and the hook switch is in the open position. When a call is received from the line, the current passes through the primary winding, causing the cam to vibrate and beat the cups. In electronic systems, this happens differently, the signal is fed to an external speaker, and at the output we hear a melody or birdsong, for example. After the subscriber picks up the phone, the call module and dialing circuit closes, and the reception opens using the relay.
Calling to another user occurs in reverse order. A person picks up the phone, which closes one circuit and disconnects another. The call is made in the dialing module by sending pulses or signals to the switching devices of the station. She, in turn, recognizes the numbers, combining them into a single number, redirects todesired point.
Voice transmission in analog systems occurs due to the vibration of the microphone membrane. In coal, it creates a seal, which causes a perturbation of the magnetic field of the coil. This oscillation generates a pulse that sends to another receiver.
Schematic design of mobile phones
The cell phone device should be singled out in a separate category, since in its execution it resembles a DECT system, but with a number of differences. It also transmits a radio signal to the receiver, but first it is encrypted. Uses its own frequencies and channels for work. But presenting a mobile gadget as a phone is not entirely correct. It has long been a multifunctional device.
If we talk about external performance, then the following should be noted:
- Form factor. It can be a folding or sliding body.
- Camera.
- Microphone.
- Speaker.
- Screen.
- Keyboard.
- USB connector.
- Battery.
- Chargers for mobile phones.
- Sim card.
Many gadgets are supplemented with various accessories, which expands their scope. Schematic diagram of the internal device is shown in the figure below.
Despite this, the device works exclusively with analog radio signals, all processes in it are fully digitized. Its chip includes analog and digital blocks.
Analog module
It includes a means of receiving and transmitting signals. Usuallylocated separately from the digital node. According to its performance, it resembles a radiotelephone, but operates according to the GSM standard. The receiver and transmitter do not work synchronously, the signal is sent with a 1/8 delay. This allows you to save battery power and integrate the amplifier with a mixer. Since the device never works for receiving and transmitting at the same time, it is a kind of switch that switches the antenna from one mode to another.
At reception, after passing through the channel filter, the signal is amplified by the LNA and sent to the mixer. It is then demodulated and sent to an analog-to-digital converter, which converts it into the digital signal needed to power the CPU.
On transmission, a logic generator modulates digital data into a signal. Further, through the mixer, it enters the frequency synthesizer, after which it passes to the channel filter and amplified one. Only a signal of sufficient strength is fed to the antenna, from where it goes into space.
Digital module
The main element and the brain of the entire system is the central processor, which processes all incoming information. The chipset of the microcircuit is used similar to a computer one, but in terms of performance and power it cannot compete with it. In addition to the CPU, this unit includes:
- An analog to digital converter that converts analog microphone signals to digital data.
- Speech and channel encoder and decoder.
- Digital-to-analog converter.
- Decoder andencoder.
- Speech activity detector. Enables nodes to operate only when the caller's speech is present.
- Terminal funds. Form a communication interface with external devices such as a PC or a phone charger.
- Wireless modules.
- Keyboard.
- Display.
- Speaker.
- Microphone.
- Camera module.
- Removable storage.
- Sim card.
Some companies use two microphones. One is needed to suppress external noise. Also, sometimes two speakers are used: one for telephone conversations, the other for playing music.
The principle of operation of mobile devices in a cellular network
Mobile phones operate on the GSM network on four frequencies:
- 850 MHz.
- 900 MHz.
- 1800 MHz.
- 1900 MHz.
The system standard includes three main components:
- Base Station Subsystem (BSS).
- Switching Switching Subsystem (NSS).
- Service and Management Center (OMC).
The device interacts with base stations (towers). After turning it on, it starts scanning networks of its standard, which it recognizes by the broadcast identifier. If available, the phone selects the station whose signal strength is higher. Next comes the authentication. Identifiers are unique SIM card numbers IMSI and Ki. Next, the Authentication Center (AuC) sends a random number to the device, which is the key for a special algorithmcomputing. At the same time, the system performs such a calculation on its own. If the results of the base and the device match, then the phone is registered on the network.
The unique identifier for the device is its IMEI, which is stored in non-volatile memory. This number is set by the manufacturer and is his passport. The first eight digits of the IMEI include the description of the device, the rest are the serial number with a check digit.
After successful registration, the phone is ready to exchange signals with base stations. As mentioned earlier, the arrangement of telephones of cellular operators is similar to the system of DECT devices, but with its own differences. Before going on the air, the mobile signal is encrypted and divided into segments of 20 ms. Encoding is performed according to the EFR standard algorithm using a public key. And the antenna is activated by a speech activity detector (VAD), that is, when a person starts talking. Speech discontinuity is handled by the codec using the DTX algorithm. At the receiving side, the signal is processed in the same way, but in reverse order.
Chargers
Chargers for mobile phones are an important component, as they keep the device functioning. Their direct purpose is to reduce the voltage and current of the mains to the required values and supply it to the battery. Basically, the output voltage is 5V, the current depends on the model and capacity of the battery. The battery charge time also depends on its strength.
Chargers share:
- Ontransformer.
- Pulse.
The first ones are not afraid of voltage drops and always have a large current margin. Their concept is very simple. The step-down coil is supplied with mains voltage, which reduces it to the desired values. The current from the second winding passes to the diode bridge, where the capacitor is installed. It acts as a filter against power surges and takes over the excess. Next, the resistor lowers the current and transfers it to the battery.
The pulse memory circuit is more complex and is made using diodes and transistors.
Support wireless data transmission systems
Currently, there are three ways to transfer data:
- Infrared.
- Bluetooth.
- Wi-Fi.
The first proved to be ineffective, so it is not used. The last two are implemented on almost all devices. Bluetooth has a short range and is mainly used for the purpose of organizing a communication interface with portable devices for the phone.
Wi-Fi is considered a more advanced format and is used to access the Internet. It should be noted that there are special software that allow you to make calls over the Internet without using a cellular connection. Also, using this technology, you can organize a local network to which several devices can connect at once and exchange data.
Optional accessories
Manufacturing companies are trying in every possible way to attract customers to their products,therefore constantly expand the range of the offered nomenclature. This includes:
- Cases.
- Glass protection.
- Portable devices for the phone, such as a headset.
- Removable drives.
- Multimedia.
- Smart tools.
- USB devices for your phone, such as cables, adapters or chargers.
Such utilities greatly expand the capabilities of gadgets and make life easier for their owners.
Comparative characteristics of modern phone models
In order to understand what modern phones are, you need to see their parameters clearly. But considering one brand is unfair. A review of one sample will not give a complete picture, therefore, for comparison and analysis, three flagship smartphones of Samsung brands (the device of phones of this brand is not too different from others), Apple and Xiaomi were taken. By price category, they lined up in the following order:
- Apple.
- Samsung.
- Xiaomi.
Judging by the price, the iPhone uses advanced technologies that have the highest parameters. However, Samsung has been on the market since 1938 and has accumulated a lot of experience. In general, the purpose of the comparison is not to identify the winner and answer the question of which is better - the device of phones on "Android" or on the iOS platform. The challenge is to show how high the technology has come.
| Parameter names | Apple | Sumsung | Xiaomi |
| Dimensions, mm | 77, 4×157, 5×7, 7 | 76, 4×161, 9×8, 8 | 74, 9×150, 9×8, 1 |
| Weight, g | 208 | 201 | 189 |
| Network Support | Samsung, Apple and Xiaomi phones support 2G, 3G, 4G networks | ||
| Sim cards | 1 non-sized | 2 nanoscale | |
| Diagonal display size, inches | 6, 5 | 6, 4 | 5, 99 |
| Screen resolution | 2688×1242 | 2960×1440 | 2160×1080 |
| DPI density | 458 | 516 | 403 |
| Production technology | OLED | Super AMOLED | IPS |
| Number of colors on screen | 16 million | 17 million | 16.7 million |
| System | iOS | Android | |
| CPU manufacturer | Apple | Samsung | Qualcomm |
| CPU model | A12 Bionic | Exynos 9810 | Snapdragon 845 |
| Number of cores | 6 | There are 8 of them in the device of Xiaomi and Samsung phones in the general configuration, 4 for each | |
| Frequency, GHz | 2, 5 | 1, 9; 2, 9 | 1, 8; 2, 8 |
| Technology, nm | 7 | 10 | |
| RAM, GB | 4 | 6 | |
| Internal memory, GB | 256 | 128 | |
| Built-in sensors |
|
|
|
| Rear camera resolution, MP |
Main: 12 MP Auxiliary: 12 MP |
||
| Aperture sensitivity |
Main: ƒ/2.4 Auxiliary: ƒ/1.8 |
Main: ƒ/2.4 Auxiliary: ƒ/1.5 |
Main: ƒ/2.4 Auxiliary: ƒ/1.8 |
| Front camera resolution, MP | 7 | 8 | 5 |
| Aperture sensitivity | ƒ/2.2 | ƒ/1.7 | ƒ/1.7 |
| Supports wireless technology | Bluetooth, Wi-Fi | ||
| Satellite Positioning | GPS, GLONASS, A-GPS | ||
| Battery capacity, mAh | 3174 | 4000 | 3400 |
| Protection systems |
|
The Samsung phone only has a face scanner | Xiaomi has a fingerprint scanner |
As can be seen from the table, the specifications and devices of Samsung, Xiaomi and Apple phones are almost the same. This only speaks of he althy competition and the desire to make your product better for users. All manufacturers are introducing the latest technologies that do not stand still and are developing rapidly.
Conclusion
Not much time has passed since the appearance of the first telephone. During this period, they have evolved from a simple set of parts to smart devices. They combine many functions that were previously assigned to other devices. And this development will continue.
