The principle of operation and the device of the phone

The device of 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 and receive messages, but also play video and audio, access the Internet, process large amounts of information, and perform many operations and tasks at the same time. What do we know about how the phone is arranged and how it works? As part of this article, we will try to understand this issue.

The Origin and Evolution of the Phone

Samuel Morse, who invented the telegraph and Morse code, is considered to be the founder of the first apparatus for transmitting information over distances.

It is difficult to call this device a full-fledged phone, since the information was transmitted using contact closure and the “Morse code” code specially developed for it, as it is often called in abbreviation.

Some historians attribute the invention of the first telephone to Antonio Meucci, which he called a telephone. He developed the drawings, but for reasons unknown to anyone, he did not register his creation. Therefore, the patent belongs to Alexander Bell. His device was without a bell and apparently had nothing to do with modern devices.

The device was cumbersome and inconvenient for negotiations, weighing about eight kilograms. However, this did not prevent its popularization and wide distribution throughout 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 vehicles. They got a handset and dial to dial a subscriber. The dial contained numbers and letters, except for the letter "Z", as it resembles a triple. On push-button stationary phones, this numbering has been preserved to this day. This is not done to send messages at all, 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 pulses.

Cordless phones appeared in our country in the 70s of the twentieth century. They transmitted a radio signal to the base, which, in turn, was connected via a line through switches to another subscriber. Their trade name is Altai, they were a prototype of mobile communications. This installation weighed seven kilograms. It was not suitable for carrying, so vehicles of operational services were equipped with it. It 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. Prices for spacecraft were cosmic, and only very wealthy 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 great functionality, including sending short messages. Initially, they were supposed to send them as service notifications, but the users liked the option so much that it turned into a separate service for mobile operators.

With the entry into the era of portable devices, mobile phone devices became more complex, sizes and weight less, and more opportunities. From three-kilogram giants, they have turned into miniature means of communication that easily fit even in the hand of a child. Over time, the real button keyboard was replaced by a virtual one on the touch screen. Cameras, fingerprint scanners, and many other devices appeared on the panel.

How are analog telephone sets

A telephone device with a disk and button dial is similar in terms of the presence of composite blocks, but differs in the principle of operation. Aggregates include the following modules:

• Handset with microphone and speaker.
• Phone.
• Calling remedy.
• Dialing node
• Transformer.
• Lever switch.
• Separation capacitor.
• Radio frequency module (portable stations).

The lever switch is responsible for connecting the device to the subscriber line. In a cordless telephone device, the connection is due to the power on of the handset of the device.

A 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 form an electromagnetic pulse from sound, passive change the parameters of other nodes, mainly capacitance and resistance. For the latter, an additional power source is required.

The phone converts 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 membrane elements of the sources of sound frequencies associated with it.

The call node can be induction and electronic. It is necessary to notify the subscriber about an incoming call. The first, with the help of the flowing current in the coils, makes the striker vibrate and strike the bell cups. The electronic unit processes information about the incoming signal and redirects it to the general speaker in the form of pulses of a given frequency, which is called the ringtone.

The RF module is present only in the cordless telephone device. It is designed to exchange information between the phone and the receiver via radio signals.

A transformer connects individual conversational nodes to each other. It also eliminates the effect of local echo in the tube and is responsible for matching with line resistance.

A separation capacitor is needed to connect the phone to the line in the mode of receiving an incoming signal and waiting for an outgoing one. Maintains high resistance to large incoming voltage and low to small.

The dialer can be pulsed (disk) and electronic (push-button). In the first embodiment, the mechanical wheel, rotating, closes the contacts and sends signals to the PBX. Their number corresponds to a specific number of the subscriber number. Electronic work through integrated circuits, which artificially generate pulses using solid state relays and send them to the receiver of the station. Modern exchanges still retain this method of calling a subscriber, but more often they use tone dialing. Modern devices also support IP-telephony. The principle of tone dialing is to generate short-term signals of preset frequencies, each value of which corresponds to a certain number of numbers. The device connecting the phone via IP involves the use of the provider's server via a dedicated Internet channel from which the call is made. Mobile devices send radio signals of a given frequency to the communication system of towers of cellular operators.

The principle of operation of devices in wired networks

In order to fully understand a mobile phone’s device, you need to know how an analog ATS system works. Despite the fact that cell phones are a complex digital structure with integrated circuits, the basic principle of ordinary stationary devices is laid in their work.

Each service provider assigns unique identification numbers to its customers by which they distinguish between them. 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 device, and the lever switch is in the open position. When a call arrives from the line, the current passes through the primary winding, forcing 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 circuit of the communication module and dialer closes, and the receiver opens by means of a relay.

A call to another user occurs in the 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 numbers by combining them into a single number, redirects to the desired point.

Voice transmission in analog systems is due to vibration of the microphone membrane. In coal, it creates a seal, which causes a disturbance in the magnetic field of the coil. Such oscillation forms an impulse, which sends to another receiver.

Schematic design of mobile phones

The cell phone device should be divided into a separate category, since in its design it resembles a DECT system, but with a number of differences. It also transmits a radio signal to the receiver, but previously encrypting it. Uses its frequencies and channels for work. But presenting a mobile gadget as a phone is not entirely correct. This has long been a multifunctional device.

If we talk about external execution, the following should be noted:

• Form factor. It can be a folding or sliding case.
• Camera.
• Microphone.
• Speaker
• Screen.
• Keyboard.
• USB connector
• Accumulator battery.
• Chargers for mobile phones.
• SIM card.

Many gadgets are supplemented with various accessories, which expands their scope. The 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 units.

Analog module

It includes a means of receiving and transmitting signals. Usually located separately from the digital node. By its performance characteristics it resembles a radiotelephone, but it works according to the GSM standard. The receiver and transmitter do not work synchronously, the signal is sent with a 1/8 delay. This saves battery power and integrates the amplifier with a mixer. Since the device never works at the reception and transmission at the same time, then it represents a certain switch, which switches the antenna from one mode to another.

At the reception, after passing through the channel filter, the signal is amplified by the LNA and sent to the mixer. Then it is demodulated and transmitted to an analog-to-digital converter, which converts it into a digital signal, which is necessary for the central processor to work.

In transmission, a logic generator modulates digital data into a signal. Then, through the mixer, it enters the frequency synthesizer, after which it passes to the channel filter and amplified. Only a signal of sufficient power is fed to the antenna, from where it goes into space.

Digital module

The main element and the brain of the whole system is the central processor, which processes all incoming information. The chipset of the microcircuit is used similar to the 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 into a digital form of data.
• The encoder and decoder of speech and channels.
• Digital to analog converter.
• Decoder and encoder.
• Speech activity detector. Provides operation of nodes only when there is a subscriber speech.
• Terminal facilities. They form an interface for communication with external devices, such as a PC or a charging device for a telephone.
• Wireless Modules.
• Keyboard.
• Display.
• Speaker
• Microphone.
• Camera module.
• Removable drive.
• SIM card.

Some companies use two microphones. One is needed to suppress external noise. Two speakers are also sometimes used: one for telephone calls, the other for music playback.

The principle of mobile devices in a cellular network

Mobile phones work in a GSM network at four frequencies:

• 850 MHz.
• 900 MHz
• 1800 MHz.
• 1900 MHz.

The system standard includes three main components:

1. Base Station Subsystem (BSS).
2. Switching Subsystem (NSS).
3. Service and Management Center (OMC).

The device interacts with base stations (towers). After switching on, it starts scanning networks of its standard, which it recognizes by the broadcast identifier. If available, the phone selects the station whose signal level is higher. Next is authentication. The identifiers are the unique SIM card numbers IMSI and Ki. Further, the authentication center (AuC) sends the device a random number, which is the key for a special calculation algorithm. At the same time, the system carries out such a calculation at home. If the results of the base and the device match, then the phone is registered on the network.

A 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 IMEI include a description of the device, the rest are a serial number with a check number.

After successful registration, the phone is ready to exchange signals with base stations. As mentioned earlier, the device of mobile phone operators is similar to the system of DECT devices, but with its own differences. Before going live, 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 begins to speak. Intermittent speech processes the codec using the DTX algorithm. At the receiving side, the signal is processed in a similar way, but in the reverse order.

Charging device

Chargers for mobile phones are an important component, because thanks to them, the device continues to function. 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 5 V, the current strength depends on the model and battery capacity. The battery charge time also depends on its strength.

Chargers share:

• On transformer.
• Impulse.

The former are not afraid of voltage drops and always have a large current margin. Their schematic diagram is very simple. Mains voltage is applied to the lowering coil, 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 excess to itself. 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 for wireless data systems

There are currently three ways to transfer data:

1. Infrared port.
2. Bluetooth
3. Wi-fi

The first proved its inefficiency, so it is not used. The last two are implemented on almost all devices. Bluetooth has a short range and is mainly used to organize the 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 allows you to make calls over the Internet without using cellular communications. Also, using this technology, you can organize a local network to which several devices can connect and exchange data at once.

Optional accessories

Manufacturing companies are trying in every possible way to attract customers to their products, so they are constantly expanding the range of products offered. These include:

• Covers.
• Glass protection.
• Portable phone devices, such as a headset.
• Removable drives.
• Multimedia Tools.
• Clever means.
• USB devices for the phone, such as cables, adapters, or chargers.

Such utilities greatly expand the capabilities of gadgets and simplify the lives of their owners.

Comparative characteristics of modern phone models

In order to understand what modern phones are, you need to see their parameters visually.But to consider one brand is unfair. A review of one sample will not give a complete picture, so for comparison and analysis we took three flagship smartphones of Samsung brands (the device of this brand of phones is not too different from others), Apple and Xiaomi. By price category, they are lined up in the following order:

1. Apple
2. Samsung
3. Xiaomi

Judging by the price, the iPhone phones use advanced technologies that have the highest parameters. However, Samsung has been present on the market since 1938 and has gained extensive experience. In general, the purpose of the comparison is not to identify the winner and answer the question of which is better - the device devices on the "Android" or on the iOS platform. The challenge is to show what heights technology has reached.

As you can see from the table, the specifications and design of Samsung, Xiaomi and Apple phones are almost the same. It only speaks of healthy competition and the desire to make their product better for users. All manufacturers introduce the latest technologies that do not stand still and are developing rapidly.

Conclusion

Not much time has passed since the first phone arrived. During this period, they have evolved from a conventional set of parts into smart devices. They combine many functions that were previously assigned to other devices. And such development will continue further.