How does a landline telephone work? How a mobile phone works
Over the past 20 years, the mobile phone has evolved from a regular means of communication into a true multifunctional device. A modern mobile phone, depending on the degree of saturation with functions, combines: a communication device, a radio receiver, music player, a camera, a voice recorder and much more, except that he doesn’t know how to cross-stitch. In fact, it has turned into such a multifaceted toy for adults. Human curiosity knows no bounds and many people naturally ask: what’s inside this toy? Of course, out of simple curiosity, I somehow don’t want to disassemble a device that costs several thousand rubles. In that case, this article is just for you!
A mobile phone is a technically complex device, the heart of which is an electronic board that ensures that the phone performs the functions assigned to it. By analogy with computers, it is often called maternal. Various devices (display, antenna, etc.) are connected to the motherboard, which ensure the interaction of the phone with the operator’s network and the user. The shape, size and design features of the phone's motherboard depend on the form factor of the phone case and the specifics determined by the phone brand. And it is advisable to start examining the design with the body - after all, it is in plain sight.
Hull parts
In modern mobile phones, cases of three main form factors are used - candybar, book (clamshell), slider, as well as their variations - flip (a hinged cover that covers the keyboard) and a rotator (parts of the case rotate relative to each other). Currently, phones of the last two form factors are very rare. Cases in the slider form factor have several design options (we will take old phone models as a basis):
- Only the keyboard moves. When closed, the keyboard blocks part of the screen. An example of such a design is.
- Only the screen moves. When closed, the screen blocks part of the keyboard. Example - .
- The screen and part of the keyboard move. Typically this part includes a joystick, soft keys, and answer and end call keys. The most common slider variation. Example - .
Naturally, the design of the phone has a direct impact on its internal structure - in phones with cases that have moving parts, there is always a flexible cable connecting the moving parts of the phone to each other. By the way, chafing (breaking) of this particular cable is one of the common malfunctions of phones with “mobile” form factors. In a number of phones, the flexible cable also includes other components - display, speakers, etc. An example of a phone with a similar cable is.
A candybar phone body usually consists of three components - the front and back panels and the middle part. The back panel is often combined with the battery compartment cover or the battery. The combination of the battery compartment cover and the battery is typical for models made in Asia and China - Samsung, LG, Pantech, Fly, etc. The middle part of the all-in-one phone body can be either visible (,) or hidden from the user (). The case of a phone with a book form factor usually includes the upper and lower parts of the case and a rotating mechanism. Phone cases of the slider form factor necessarily include a slide along which the parts of the case slide relative to each other. In turn, the upper and lower parts of the bodies of “books” and “sliders” usually consist of two or three parts. Also, the display glass can be distinguished as a separate part of the body.
The keyboard in cell phones of any form factor consists of two parts. The first one visible to the user is usually plastic keys on a flexible substrate. The second of them is hidden and consists of a substrate with metal plates that close the contacts on the keyboard board. Structurally, the keyboard board can be either combined with the motherboard or separate from it (). In some phones, the keyboard board and its substrate are combined with a flexible cable ().
Battery
The battery is the most important component of a mobile phone, because it is what ensures its functioning. By type, batteries used in mobile phones are nickel-metal hydride (Ni-Mn, used in older phone models, have a memory effect), lithium-ion (Li-On), lithium polymer (Li-Pol). Nickel-metal hydride batteries for mobile phones usually consist of three rechargeable batteries of a round () or square () shape.
Lithium-ion and lithium polymer batteries usually consist of one battery and an electronic unit. The functions of the electronic battery unit of these types are to protect the battery from deep discharge(less than 3 V) or overcharge (more than 4.2 V). Without going into technical terminology, this block is an electronic switch that breaks the circuit of one of the battery terminals. It is the presence of this block that explains the fact that a phone that has not been used for a long time may not turn on and refuses to charge.
Display
Mobile phones are equipped with displays of various types - black and white and color, made using STN, UFB, TFT, OLED and other technologies. Naturally, displays made using different technologies, have differences in image quality, however, from the point of view of design, phone displays can be divided into two groups - those connected to the board through a connector located on a flexible cable and those soldered to it (,). In phones with slider or book form factors, they often use a so-called display module - a display (or two displays) on one board. All the auxiliary components necessary for operation are soldered onto the same board. display module and a connector for connecting a flexible cable. By the way, due to the use of the display module, replacing the display in phones with book or slider form factors costs more than similar work in all-in-one phones. The display module may also include phone speakers
Other mechanical parts
The phone also includes a microphone, conversational and polyphonic speakers, a camera, and a vibration motor. The functional purpose of these blocks is quite clear. In a number of phones, the same speaker can be used to talk and play a melody. Speakers in phones can be hard-soldered to the motherboard, but more often than not, they are fixed to the body of the phone and connected to the motherboard through a connector or group of spring-loaded pins. Connecting microphones to the motherboard of phones is carried out in a similar way. However, in phones from Asian-Chinese manufacturers there is often a situation where the microphone is soldered to the motherboard. The camera is usually also connected to the phone’s motherboard through a connector, which can be of two types – flexible and rigid.
One of the most important parts of a mobile phone is the antenna. Currently, the vast majority of phones are equipped with an antenna located inside the case. Structurally, the antennas of most phones are a pin or a plate of a special shape. The shape of the pin is more typical for external antennas, (), although there were also internal antennas similar kind (). It is the location of the antenna and the distance from it to the brain, as well as the radiation power of the phone, that determine its potential danger to human health. There is fierce debate about how real this harm is, but doubters may want to choose a phone with an antenna as far away from the ear as possible. In this regard, folding phones compare favorably, since their antenna is usually located at the bottom of the case. The Motorola RAZR V3 is especially advantageous in this regard - its antenna is located near the microphone and, therefore, as far as possible from the brain.
Summarizing
The article discusses the main mechanical parts that make up a mobile phone. Naturally, this consideration is very generalized, but based on it we can draw up general idea how this toy for adults works. More detailed description The procedure for disassembling the phone, a list of its mechanical parts and the method for replacing them are described in the Service Manual, which is essentially a repair manual intended for service centers. I hope my short review will be useful to you, but solely for replenishing your general knowledge.
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Posted by: Sergey.
Hello, I wanted to ask if I order a phone from an online store, will it arrive by mail intact and safe? Or will it be a little crippled? I want to buy exactly the one I need, but I'm afraid.
Posted by: t.n.
thank you very much! This material helped prepare a report on physics for 7th grade.
Posted by: Gloomy
An article for those who are far from this, but want to find out... Just like in the first grade, when they lead you by the hand and tell you, you learn this and that here. If I am a purely technical person, I immediately liked the fact that the basics came to mind, and the rest needs to be developed and found!!! And it’s not worth blaming the author for saying that someone is a genius.... There are enough of them on TV!!! And now for the smart ones, give me a link where to develop further.... OKAY
Posted by: ku
What is the difference between the percentage of a regular phone and a “smart” phone? I don’t mean “power” and clock frequency.
Written by: Anton Pecherovy
Dear IONe, the story about the operation of a mobile phone will be replete with technical details that most people are not interested in. I agree, this article is a review intended for people far from technology. A detailed story about the design of a mobile phone will require more than one article, because you will have to remember a bunch of physical laws on which it all works, the basics of electronics and programming. In short, a mobile phone is a microprocessor device operating under the control of a control program ( operating system). It also contains various “peripherals” - a transmitting and receiving path, a microphone, a speaker, a display, a camera, etc. Correct operation with all these devices is ensured software device - firmware and calibration data (constants written at the factory into the phone’s memory). If you are interested in more specific information, please refer to specialized literature.
Now about your problem - it’s difficult to advise anything remotely. Try checking the battery voltage with a multimeter. A fully charged battery has a voltage of about 4.2 V. If it is less, try charging it in your phone or with a “frog” (universal charger for all battery sizes)
Written by: Anton Pecherovy
I will answer point by point:
Andrey, whether or not you see the presence of practically useful information in this article is up to you. I won’t comment on “idiot” and “ram”. If you are interested in a specific Technical information refer to specialized literature, preferably the original source. Finding a description of the GSM standard is not a problem. But as for “literate people” - excuse me, you are not one of them. A competent person works with specialized literature and does not throw around insults and sweeping accusations. Judging by the comment, your level of knowledge is at the level of the sites that you advised me to write.
Posted by: IONe
Dear Anton, I cannot but agree with Andrey, who criticizes you. Information for a teapot, could you tell us how this or that part of the mobile phone works!
I also wanted to ask a question. I found an old Nokia 2300 in my drawer and tried to turn it on - it works! But my joy did not last long, after 1 minute it went out. Again I tried to turn it on, it works and again after 1 minute it goes out. I took it apart and looked at the contacts, they are fine, the battery is full (tongue tingles))) What could it be - I would like to make a mobile phone, I really like the polyphone even though it has 4 voices - classic!!1
Posted by: Andrey
All of the above concerns only the phone body and does not provide any useful information about its operation and use. This is from that series like a book: “Windows 95 in 10 minutes.” Such books are written by idiots and for idiots. Because Windows was developed by a group of several thousand over the course of one year, and only an idiot would think that he could figure it out in 10 minutes. So here I can well call the author about the design of a mobile phone an IDIOT. Don't go into the area where you are a RAM. Better write porn sites and don’t fool literate people, we don’t have time to read the misinformation of all sorts of IDIOTS.
Posted by: Andrey
What is the wavelength of electromagnetic vibrations from mobile phones. How are channels selected for phones? How it works oscillatory circuit and antenna. What is the emitted power of the phone. How is it possible to say this while in a bus or car? Apparently the EM field strength in this area is very high?
The composition of telephone sets intended to operate in telephone networks, includes the following required elements: microphone and telephone combined into a handset, ringing device, transformer, isolation capacitor, dialer, lever switch. On fundamental electrical diagrams The telephone set is designated by the letter E.
Let's briefly look at the purpose of the main elements of a telephone.
The microphone is used to convert the sound vibrations of speech and the electrical signal of sound frequency. Microphones can be carbon, condenser, electrodynamic, electromagnetic, piezoelectric. They can be classified into active and passive. Active microphones directly convert sound energy into electrical energy. In passive microphones, sound energy is converted into a change in some parameter (most often capacitance and resistance). To operate such a microphone, an auxiliary power source is required.
In mass-produced telephone sets, as a rule, carbon microphones are used, in which, under the influence of sound waves the electrical resistance of the carbon powder located under the membrane changes. The most widely used microphone capsules are types MK-10, MK-16, which have a fairly high sensitivity (the described devices mainly use carbon microphones). On circuit diagrams microphone represent with Latin letters VM.
It should be noted that in Lately A number of telephone sets are also equipped with condenser microphones of the types MKE-3, KM-4, KM-7.
A telephone is a device designed to convert electrical signals into sound and designed to operate under conditions of stress on the human ear. Depending on the design features telephones are divided into electromagnetic, electrodynamic, with a differential magnetic system and piezoelectric. In telephone sets, electromagnetic type telephones are most widespread. In such phones, the coils are fixed. Under the influence of the current flowing in the coils, an alternating magnetic field arises, driving a movable membrane, which emits sound vibrations. In modern telephone sets they are used in
mainly telephone capsules of the TK-67 type, and in devices of outdated designs - also TK-47 and TA-4.
The operating frequency band for microphones and telephones used in telephone sets is approximately 300...3500 Hz. On circuit diagrams, the telephone is designated by the Latin letters BF.
For ease of use, the microphone and telephone are combined in a handset.
The ringing device is used to convert ringing signal alternating current into the sound signal. Electromagnetic or electronic ringing devices are used. The first of these is a single or double coil bell. The sound signal is formed as a result of the striker hitting the bell cups. The current flowing in the coils with a frequency of 16...50 Hz will create an alternating magnetic field, which sets the armature with the striker in motion. As a rule, telephone calls use permanent magnets that create a certain polarity of the magnetic circuit, which is why such calls are called polarized. The resistance of the bell windings to direct current is 1.5...3 kOhm, the operating voltage is 30...50 V. On the circuit diagrams, the bell is designated by the Latin letters HA.
An electronic ringing device converts the ringing signal into an audio tone that can imitate, for example, a bird singing. A telephone or a piezoelectric ringing device VP-1 is used as an acoustic emitter. Such ringing devices are used, for example, in modern telephone sets TA-1131 “Lana”, TA-1165 “Stella”, etc. Electronic ringing devices are made using transistors.
The telephone transformer is designed for communication individual elements conversational part and to match their resistances with the input resistance of the subscriber line. In addition, it allows you to eliminate the so-called local effect, which will be discussed below. Transformers are made with separate windings or in the form of autotransformers.
The separating capacitor serves as an element for connecting the calling device to the subscriber line in standby and call receiving mode. This ensures an almost infinitely high resistance of the telephone to direct current and low resistance to alternating current. In telephone sets, isolation capacitors of the MBM and K73-P types are used with a capacity of 0.25...1 μF and a rated voltage of 160...250 V.
The dialer supplies dialing pulses to the subscriber line in order to establish the required connection. Pulses are used to periodically close and open the line. Modern telephones use mechanical and electronic dialers. A rotary mechanical dialer has a disk with ten holes. When the disk is rotated clockwise, the spring of the dialer mechanism is wound up. After releasing the disk, it rotates in the opposite direction under the action of a spring, and the contacts that switch the subscriber line periodically open. The required speed and uniformity of rotation of the disk is achieved by the presence of a centrifugal regulator or friction mechanism. The formation of pulses with free movement of the disk ensures their stable frequency and the required interval between pulse parcels corresponding to two adjacent digits of the dialed number. The required interval is ensured due to the fact that the number of openings of the pulse contacts is always selected one or two more than the number of pulses required to be supplied to the line. This ensures a guaranteed pause between bursts of pulses (0.2...0.8 s). In this case, these extra pulses do not enter the line, since at this time the pulse contacts are shunted by one of the groups of dialer contacts. There are also contacts that close the phone when dialing a number to eliminate unpleasant clicks. The frequency of pulses generated by the dialer should be (10±1) pulses/s. The number of wires connecting the dialer to other elements of the telephone can be 3 - 5.
Electronic dialers, which are equipped with many modern telephone sets (for example, TA-5, TA-7, TA-101), are made on integrated circuits and transistors. The number is dialed by pressing the keyboard buttons - the so-called keypad. Since the speed of pressing buttons can be as high as desired, on average 0.5 seconds are saved on dialing one digit of a number. In addition, keypad dialers provide users with various time-saving conveniences:
remembering the last dialed number, the ability to remember several dozen numbers, etc. Electronic dialers are powered both from the subscriber line and from a 220 V network through a power supply.
The lever switch provides connection to the subscriber line of a telephone ringing device in an inoperative state (the handset is on) and conversation circuits or a dialer in a working state (the handset is off-hook). A lever switch is a group of several switching contacts that are activated when the telephone is picked up.
In addition to the listed elements, the telephone set also includes resistors, capacitors, diodes, and transistors that form the speaking circuit of the device.
Let's consider the device of the telephone set (TA) as a whole.
When the telephone is operating in conversational mode, a local effect occurs, i.e. listening to your own speech on your phone. The local effect is explained by the fact that the current flowing through the microphone flows not only into the subscriber line, but also into your own telephone. To eliminate this undesirable phenomenon, anti-local devices are used in modern telephone sets.
There are different types similar devices. Let's consider one of them - a bridge-type anti-local device (Fig. 1).
Microphone VM1, telephone BF1, balanced circuit Zb and line Zl are interconnected by the windings of transformer T1: linear I, balanced II and telephone III. During a conversation, when the resistance of the microphone changes, conversational audio frequency currents flow through two circuits: linear and balanced. It is clear from the diagram that the currents flowing through windings I and II are summed with opposite signs, so there will be no current in winding 111 if the currents in the linear and balanced windings are equal in magnitude. This is achieved by appropriate selection of elements of the balance circuit Zb, the parameters of which depend on the parameters of the line Zl. The line resistance contains active and capacitive components, so the balanced circuit is made of resistors and capacitors.
Complete elimination of the local effect is achieved only at one specific frequency and certain line parameters, which is impossible in real conditions, since the speech signal contains a wide range of frequencies, and the line parameters vary widely (depending on the distance of the subscriber from the telephone exchange, transition resistances and capacitances in the cables etc.), therefore in practice the local effect is not completely destroyed, but only weakened.
Let's consider the diagram of the TA-72M-5 telephone set (Fig. 2), designed for operation in urban networks. Its switching and calling part consists of a lever switch SA1, a bell HA1, a separating capacitor C1 and a dialer SA2. The speaking part of the telephone consists of telephone BF1, microphone VM 1, transformer T 1, balanced circuit (capacitors C1 and C2, resistors R1-R3) and limiting diodes VD1, VD2. The speaking part is made according to a counter-bridge type scheme.
In the initial state of the contacts of the lever switch SA1 and the dialer SA2, shown in the diagram, the bell HA1 and capacitor C1 connected in series are connected to the line, and the speaking part is turned off. When ringing voltage appears at terminals 1 and 4 of the telephone set, current flows through the circuit: terminal 1 - jumper - terminal 3 - bell winding - normally closed contacts SA1.2 of the lever switch - capacitor C1 - terminal 4. (The direction of the current is chosen conditionally - with this it could also be considered flowing from terminal 4 to terminal 1.) Having heard the call, the subscriber picks up the phone. In this case, contacts SA1.1 and SA1.2 switch to another position, turning off the calling circuit and connecting the speaking circuit to the line. The DC resistance between terminals 1 and 4 varies from very high (hundreds of kilo-ohms - mega-ohms) to relatively small (hundreds of ohms), this is recorded by the telephone exchange devices, and they switch to conversational mode.
When dialing a number, the contacts SA2.1 of the dialer are in a closed state during forward and reverse rotation of the disk, which provides bypassing of the conversational circuit and eliminates the possibility of listening to clicks on the phone. When the dialer rotates back, the contacts SA2.2 break the linear circuit, and the station devices record the number of the called subscriber based on the number of such breaks.
Diodes VD1 and VD2 limit voltage surges on the phone windings and eliminate sharp sounds that are unpleasant to the ear.
For networking telephone exchanges manual maintenance uses telephones without a dialer. The diagram of one of these devices (type TA-68CB-2) is shown in Fig. 3. Its main difference from the previous device is the absence of dialer contacts and one group of lever switch contacts, due to which the bell and capacitor C1 remain connected to the line in conversation mode. However, they have virtually no effect on the operation of the telephone in this mode.
In the telephone communication devices described in this book, you can use industrially produced telephone sets both with a dialer (TA-68, TA-72M-5, TA-1146, etc.) and without it (TA-68CB-2 and others similar). But telephones without a dialer are only suitable for manual telephone switchboards. If a radio amateur has a telephone set at his disposal, in which only the handset and bell are working, it can also be used. In this case, the elements are connected in accordance with the diagram shown in Fig. 4. Capacitor C1 - type K73-17, MBM, MBGO. It should be noted that in such a telephone set the local effect will be fully manifested, but for the sake of simplicity, you can sacrifice some convenience.
Let's take a brief look at how telephone lines are switched in city PBXs. Since 1876, when the Scotsman A.G. Bell invented the world's first two-wire telephone, the principle of telephone communication has not undergone significant changes.
The diagram for organizing telephone communication between two subscribers is shown in Fig. 5. Power supply current for telephone sets El, E2 pro-
goes through chokes L1 and L2. Chokes are necessary to prevent the conversational (alternating) current from shorting through the power source direct current Upit, the internal resistance of which is very small and amounts to fractions of an ohm. The direct current source is usually called the central battery (CB). Chokes L1 and L2 have a relatively low DC resistance (usually no more than 1 kOhm). The inductance of the chokes is quite large and in the frequency range of conversational currents (300...3500 Hz) it will create such significant resistance to the conversational (alternating) current that it practically does not branch into the central bank and flows in the circuit between devices E1 and E2. On automatic telephone exchanges, the windings of two-winding relays are usually used as chokes, and these relays simultaneously serve to receive a signal about a call to the station by the subscriber and a signal to end the call (hang up).
The inductor generates an alternating ringing voltage with a frequency of 16...50 Hz, which activates the ringing device of the desired telephone set.
Subscriber switching was initially carried out manually on the PBX, then step finders began to be used, and currently switching is carried out by quasi-electronic or electronically. PBX switching devices controlled by impulse
direct current signals, which are created by the telephone dialer when the subscriber dials the digits of the called subscriber’s number.
Figure 6 illustrates the simplest principle of establishing a connection on a PBX. The telephone set of the first subscriber E1 is connected to the central bank (Upit) through the windings of the two-winding relay K1. When the first subscriber picks up the handset of the E1 device, relay K1 is activated and contacts K 1.2 supply power to the winding of relay K2. This relay is designed in such a way that the armature is not released immediately after the voltage is removed from its winding, but with some delay (in in this case this delay is about 0.1 s). Relay contacts K2.2 prepare the power circuit for the stepper short circuit detector. When the E1 subscriber dials the number of the called subscriber, the power circuit of the K1 relay windings will be interrupted by the contacts of the E1 telephone dialer (this occurs when the dialer dial moves back). Contacts K1.1 supply power pulses to the winding of the stepper short-circuit detector according to the number of the called subscriber. After the E1 telephone dialer has finished rotating, the step finder contacts will connect the caller's line to the callee's line, after which the subscribers will be able to carry on a conversation.
When, at the end of the conversation, the subscriber puts the handset on the E1 device, relay K1 will release, its contacts K 1.2 will open the power circuit of relay K2, which will also release after 0.1 s. In this case, through contacts K2.1, KZ.4 and KZ.3, power will be supplied to the winding of the stepper short circuit detector. Contact KZ.4 slides along the solid lamella of the step finder and opens only when the step finder returns to its initial state. Contact KZ.3 is a self-interrupting contact of the stepper finder, which interrupts the power supply circuit of the winding of the stepper finder when the armature is attracted to the core.
nick. Thanks to this contact, a series of pulses are formed on the short-circuit winding, which sequentially set the short-circuit contacts.1 and short-circuit.2 to their original position.
The accuracy of the operation of the subscriber relays and the step finder depends on the opening time of the dialer contacts, which should not exceed 0.1 s. Otherwise, when contacts K 1.2 open, relay K2 will not be able to hold the armature, and the connection will not occur. Therefore, the parameters of telephone dialers must meet the following requirements:
1) dialer pulse frequency 10±1 pulse/s;
2) pulse repetition period 0.95...0.105 s;
3) a pause between series of pulses of at least 0.64 s;
4) the ratio of the opening time to the closing time of the dialer pulse contact, called the pulse coefficient, depending on the type of telephone exchange 1.3...1.9.
The central battery of the telephone exchange supplies the subscriber lines with a constant voltage Upit = 60 V. When the handset of the telephone set is removed, the telephone exchange line becomes loaded with the internal resistance of the telephone set, as a result the voltage at the line terminals drops to 10...20 V (depending on the distance of the subscriber depending on the telephone exchange and the type of device used). The internal resistance of a telephone set when the handset is off-hook can be 200...800 Ohms, and the operating (conversational) current through the device can be 20...40 mA. The resistance of the telephone exchange reduced to the subscriber sockets, which includes the resistance of the line, relay windings K1 (see Fig. 5) and the internal resistance of the central battery, can range from 600 Ohms to 2 kOhms.
For a telephone with a rotary dialer, dialing a subscriber's number is carried out as follows: by rotating
dial clockwise to the finger stop, the contacts of the dialer close the line, and during reverse rotation the line opens the number of times that corresponds to the dialed digit. In Fig. Figure 7 shows a time diagram of the operation of the telephone.
It is used as a ringing signal on the PBX. AC voltage 80...120 V with a frequency of 16...30 Hz.
In the telephone communication devices described in the book, two methods are used to connect telephone lines: parallel and serial (Fig. 8).
Scheme with parallel connection telephone sets was discussed above (Fig. 5). The difference between the diagram shown in Fig. 8a, is that instead of two inductors, a current stabilizer CT is switched on, i.e. a two-terminal network, the current through which remains unchanged when the parameters of the external circuit change within certain limits.
In any case, the relation L1 + L2 = L= const is valid. therefore, a change in current in the circuit of the first subscriber causes exactly the same change in current in the circuit of the second subscriber, but with the opposite sign. This ensures the highest possible conversation volume. In practice, in intercoms, instead of a current stabilizer, you can use a resistor with a resistance of 1...5 kOhm, however, it should be taken into account that the volume of the conversation will decrease somewhat.
In Fig. 8.6 shows a diagram of the serial connection of telephone sets. With this connection, the conversational current of one device flows completely through the second device, which ensures the maximum possible conversation volume (under given conditions).
It should be noted that in city PBXs the serial method of connecting telephone lines is not used due to the complexity of switching devices. (In the book, this method is used in intercoms and manual switchboards.)
Articles and Lifehacks
In our article we will briefly examine the internal structure of a modern mobile phone, focusing on each of the significant blocks.
We are talking specifically about push-button “tubes”; we will talk about the structure of a smartphone another time.
Case and keyboard
Today, almost all push-button models are produced in a plastic case.The only exceptions are some designer phones, for example, titanium gadgets, but they can be ignored due to their low prevalence.
The vast majority of phones today are produced in the form factor; various clamshells and sliders have almost disappeared from the market. In them, the back panel is removable and often replaceable.
Thus, the user gets access to a slot for a SIM card, memory cards and battery.
The keyboard is most often made of rubber; usually the keys are backlit, making it easier to use the device in the dark.
Display
The screens of most modern push-button models are made using .Logic block
A mobile phone, like a smartphone, is a specialized minicomputer. However, the element base it uses is completely different, so you won’t find the Qalcomm or MediaTek processors familiar to touch gadgets in handsets.Moreover, model specifications almost never indicate either the type of chipset or even the amount of RAM.
The only thing that makes sense to talk about is the built-in storage, intended mainly for photos and music.
In addition, many cell phones support microSD cards, usually with a capacity of up to 32 GB. However, no more is required.
Special mention should be made non-volatile memory, which stores the device’s unique code – IMEI.
Radio module
In addition to voice communication using the GSM standard, push-button devices are capable of surfing the Internet using GPRS technology.
Its data exchange speed is extremely low even in comparison with 3G, not to mention LTE, and operator tariffs make such communication completely unusable.
To ensure stable communication, the phones have an internal whip antenna.
Sometimes you can find models that support 3G Internet. This somewhat expands the capabilities of the device.
Audio system
In its simplest form, it consists of a microtelephone and a microphone, allowing you to use the gadget for its intended purpose - for conversations.An almost integral part of the internal structure of any mobile phone is a special 3.5 mm headphone jack.
Some models also have a speaker that can be used for both hands-free communication and music playback.
SIM card
The SIM card represents the subscriber authentication key. Unlike smartphones, most handsets still use the mini-SIM standard.
There can be either one or two slots. The latter is more common in models equipped with a 3G module, so that you can separately connect a card for the Internet.
Camera
Unlike smartphones, not every phone has a camera. And where it does exist, its resolution is very modest - 0.3 megapixel modules are still found, at best you can hope for 3 megapixels.Nothing surprising - you can hardly hope to find a two-module camera with optical zoom in a device for 2 thousand rubles. Therefore, you should not count on receiving high-quality photos in this case.
Battery
The battery provides power to all elements of the mobile device. Usually it is removable, to remove it you just need to remove it back panel. IN modern models There are two types of batteries used: lithium-ion and lithium-polymer.The latter are considered somewhat more progressive, since they were created in response to the tendency of lithium-ion batteries to swell and even explode.
As a result, the problems with push-button devices in this regard are the same as with smartphones: fear of cold and limited number charge cycles.
Some users are still captivated by myths and believe that the battery has the so-called. "memory effect". There is nothing like this in modern phones.
The voltage used in modern models is usually 3.6 V.
Interfaces
This element is designed to interact with other devices.
Three options are possible:
- Complete absence of interfaces in the most primitive models.
- Bluetooth wireless interface that allows you to exchange files, for example, with another phone, desktop computer or laptop.
- A USB port that allows you to connect your phone to a PC using a cable.
Wi-Fi, which is usual for smartphone users, is absent in this case.
Other items
IN push-button phones There are several internal devices that are not usually found in smartphones. This could be a flashlight or a vibrator that allows you to receive calls without turning on the call signal.In all other respects, these gadgets are practically no different from each other.
Finally
As you can see, in the decades since the advent of cellular communications, the design of telephones has not changed much.And, despite the dominance of smartphones in the mobile market, this category of devices is still not going to die out.
It has occupied a niche that meets the needs of those who do not require anything from the device other than its main function - the ability to talk with the interlocutor.
And if earlier push-button models appeared that had a claim to compete with touch-sensitive ones, today everything superfluous has disappeared from their design, leaving only minimum required.
This allowed us to reduce the price of the device to an absolute minimum.
Almost everyone used a cell phone, but few people thought about how it all works? In this literary opus we will try to consider how communication occurs from the point of view of your telecom operator.
When you dial a number and start calling, well, or someone calls you, your device communicates via radio channel with one of the antennas of the nearest base station.
Each of the base stations contains from one to twelve transceiver antennas, directed in different directions, to provide communication to subscribers from all directions. In professional jargon, antennas are also called “sectors”. You yourself have probably seen them many times - large gray rectangular blocks.
From the antenna, the signal is transmitted via cable directly to the control unit of the base station. The set of sectors and a control block is usually called - BS, Base Station, base station. Several base stations, whose antennas serve a specific territory or area of the city, are connected to a special unit - the so-called LAC, Local Area Controller, often simply called controller. Up to 15 base stations are usually connected to one controller.
In turn, the controllers, of which there may also be several, are connected to the very central “brain” unit - MSC, Mobile services Switching Center, Control Center Mobile services , popularly known as switch. The switch provides access (and input) to city telephone lines, to other cellular operators, and so on.
That is, in the end the whole scheme looks something like this:
Small GSM networks use only one switch; larger ones, serving more than a million subscribers, can use two, three or more M.S.C., united with each other.
Why such complexity? It would seem that you could simply connect the antennas to the switch - and that’s it, there would be no problems... But it’s not so simple. It's all about one simple English word - handover. This term refers to handover in cellular networks. That is, when you are walking down the street or driving a car (train, bicycle, roller skates, asphalt paver...) and at the same time talking on the phone, then in order for the connection not to be interrupted (and it is not interrupted), you need to switch in time Your phone from one sector to another, from one BS to another, from one Local Area to another, and so on. Accordingly, if the sectors were directly connected to the switch, then all these switchings would have to be managed by the switch, which already has something to do. A multi-level network design makes it possible to evenly distribute the load, which reduces the likelihood of equipment failure and, as a result, loss of communication.
Example - if you and your phone move from the coverage area of one sector to the coverage area of another, then the BS control unit handles the transfer of the phone, without affecting the “superior” devices - L.A.C. And M.S.C.. Accordingly, if the transition occurs between different B.S., then it is controlled L.A.C. and so on.
The operation of the switch should be considered in a little more detail. A switch in a cellular network performs almost the same functions as a PBX in wired telephone networks. It is he who determines where you are calling, who is calling you, is responsible for the operation of additional services, and, in the end, in general, determines whether you can call or not.
Let's stop at the last point - what happens when you turn on your phone?
Here, you turn on your phone. Your SIM card has a special number called IMSI – International Subscriber Identification Number. This number is unique for every SIM card in the world, and it is precisely by this number that operators distinguish one subscriber from another. When you turn on the phone, it sends this code, the base station transmits it to LAC, LAC– to the switch, in turn. Here two additional modules associated with the switch come into play - HLR, Home Location Register And VLR, Visitor Location Register. Respectively, Register of Home Subscribers And Register of Guest Subscribers. IN HLR are stored IMSI all subscribers who are connected to this operator. IN VLR in turn, contains data about all subscribers who are currently using the network of this operator. IMSI transferred to HLR(of course, in a highly encrypted form; we will not go into detail about the features of encryption, we will only say that another block is responsible for this process - AuC, Authentication Center), HLR, in turn, checks whether he has such a subscriber, and, if so, whether he is blocked, for example, for non-payment. If everything is in order, then this subscriber is registered in VLR and from now on can make calls. Large operators may have not one, but several working in parallel HLR And VLR. Now let’s try to display all of the above in the figure:
Here we briefly looked at how the cellular network works. In fact, everything there is much more complicated, but if we describe everything as it is in detail, then this presentation may well exceed “War and Peace” in volume.
Next, we will look at how (and most importantly, why!) the operator debits money from our account. As you’ve probably already heard, there are three different types of tariff plans - the so-called “credit”, “advance” and “prepaid”, from English Pre-Paid, that is, prepaid. What's the difference? Let's look at how money can be written off during a conversation:
Let's say you called somewhere. It was recorded on the switchboard that subscriber such and such called there and talked for, say, forty-five seconds.
The first case is that you have a credit or advance payment system. In this case, the following happens: data about your and other calls is accumulated in the switch and then, in the order of the general queue, is transmitted to special block, called Billing, from English to bill - to pay bills. Billing is responsible for all issues related to subscribers' money - calculates the cost of calls, writes off subscription fees, writes off money for services, and so on.
Information transfer speed from M.S.C. V Billing depends on how much computing power you have billing, or, in other words, how quickly he manages to convert technical data about calls made into direct money. Accordingly, the more subscribers talk, or the more “slow” the billing, the slower the queue will move, and accordingly, the greater the delay between the conversation itself and the actual debiting of money for this conversation. This fact is associated with the dissatisfaction often expressed by some subscribers - “They say they are stealing money! I didn’t speak for two days - a certain amount was written off...” But it does not take into account at all that for conversations that took place, for example, three days ago, the money was not immediately written off... Good people they try not to notice... And these days, for example, billing could simply not work - due to an accident, or because it was somehow modernized.
In the opposite direction - from billing to M.S.C.- there is another queue in which billing informs the switchboard about the status of subscribers' accounts. Again, a fairly common case - the debt on the account can reach several tens of dollars, but you can still make phone calls - this is precisely because the “reverse” queue has not yet arrived and the switchboard does not yet know that you are a malicious defaulter and You should have been blocked a long time ago.
Advance tariffs differ from credit tariffs only in the method of settlement with the subscriber - in the first case, a person deposits some amount into the account, and money for calls is gradually deducted from this amount. This method is convenient because it allows you to plan and limit your communication costs to some extent. The second option is credit, in which the total cost of all calls for any period (“ billing cycle"), usually per month, is issued in the form of an invoice that the subscriber must pay. The credit system is convenient because it insures you against those cases when you urgently need to make a call, but the money in your account suddenly runs out and your phone is blocked.
Prepaids are designed completely differently:
In the prepaide billing as such is usually called " Pripad platform».
Immediately at the moment the telephone connection starts, a direct connection is established between switch And prepaid platform. No queues, data is transmitted in both directions directly during the conversation, in real time. In connection with this, prepaids have the following characteristic features: the absence subscription fee(since there is no such thing as billing period), a limited range of additional services (they are technically difficult to charge in “real time”), the inability to “go into the red” - the conversation will simply be interrupted as soon as the money in the account runs out. Clear dignity preipedes is the ability to accurately control the amount of money in the account, and, as a result, your expenses.
IN preipedes sometimes a funny phenomenon is observed - if prepaid platform for some reason refuses to work, for example, due to overload, then, accordingly, for subscribers prepaid tariffs at this time all calls become absolutely free. Which, in fact, makes them – the subscribers – happy.
But how is our money calculated when we talk while in roaming? And how does the phone generally work in roaming? Well, let's try to answer these questions:
Number IMSI consists of 15 digits, and the first 5 digits, the so-called СС – Country Code(3 digits) and NC – Network Code(5 digits) – clearly characterize the operator to which the subscriber is connected. According to these five numbers VLR finds the guest operator HLR home operator and looks in it - but, in fact, can this subscriber use roaming with this operator? If yes, then IMSI is registered with VLR guest operator, and in HLR home - link to the same guest VLR to know where to look for the subscriber.
The situation with writing off money in billing is also not very simple. Due to the fact that calls are processed by the guest switch, but the “home” switch counts the money billing, large delays in debiting funds are quite possible - up to a month. Although there are systems, for example, “ Camel2”, which even in roaming work on the prepaid principle, that is, they write off money in real time.
Here another question arises - what is the money written off for? roaming? If “at home” everything is clear - there are clearly defined tariff plans, then with roaming the situation is different - a lot of money is written off and it is not clear why. Well, let's try to figure it out:
All phone calls in roaming are divided into 3 main categories:
Incoming calls – in this case, the cost of the call consists of:
Cost of an international call from home to a guest region
+
Cost of an incoming call from a guest operator
+
Some surcharge depending on the specific guest operator
Outgoing call home:
Cost of an international call from the guest region to home
+
Cost of an outgoing call from a guest operator
Outgoing call to guest region:
Cost of an outgoing call from a guest operator
+
Some surcharge depending on the specific operator
As you can see, the cost of calls in roaming depends only on two things - on which operator the subscriber is connected to at home and which operator the subscriber uses when away. This reveals one very important thing - the cost of a minute in roaming absolutely does not depend on the tariff plan chosen by the subscriber.
I would like to add one more remark - if two phones of one operator are roaming together with another operator (well, for example, two friends went on vacation), then it will be very expensive for them to talk to each other - the caller pays as for outgoing home, and the recipient pays the call is like someone coming from home. This is one of the disadvantages of the GSM standard - that communication in this case goes through the house. Although technically it is quite possible to arrange a connection “directly”, which operator will do this if you can leave everything as it is and make money?
Another question that has recently often interested owners of more than one mobile phone is how much will a forwarded call from one phone to another cost? And it’s quite possible to answer this question:
Let’s say call forwarding is set from phone B to phone C. A call is made from phone A to phone B - accordingly, the call is forwarded to phone C. In this case, they pay:
Phone A – as for outgoing to phone B
(actually, this is logical - after all, that’s what he’s calling)
Phone B – pays the forwarding price
(usually a few cents per minute)
+
the cost of an international call from the region where B is registered to the region where C is registered
(if the phones are from the same region, then this component is zero).
Phone C – pays as for incoming calls from phone A
In conclusion, I would like to mention one more subtle point - how much will forwarding in roaming cost? And here's where the fun begins:
For example, your phone has a call forwarding to your home number due to busy conditions. Then at incoming call the so-called “ roaming loop" - the call will go to home phone via guest switch, accordingly, the cost of such a forwarded call for roamer will be equal to the sum of the costs of incoming and outgoing calls to home plus the cost of the forwarding itself. And what’s funny about this is that the roamer may not even know that such a call took place, and subsequently be surprised when he sees the bill for communication.
This leads to practical advice - when traveling, it is advisable to disable all types of forwarding (you can leave only unconditional - in this case, a “roaming loop” does not work), especially forwarding to voicemail- otherwise, later you can wonder for a long time - “Where did that money go, huh?”
List of terms used in the text:
AuC– Authentification Center, Authentication Center, is responsible for encoding information when transmitted over the network and received from the network
Billing– Billing, operator’s cash accounting system
B.S.– Base Station, base station, several transceiver antennas belonging to one control device.
Camel2– one of the Prepaid systems, which implements instant debiting of funds in roaming
CC– Country Code, country code in GSM standard(for Russia – 250)
GSM– Global System for Mobile Communications, the most widespread cellular communication standard in the world
Handover – transfer of handset control from one antenna/base station/LAC to another
HLR– Home Location Register, a register of home subscribers, contains detailed information about all subscribers connected to this operator.
IMEI– International Mobile Equipment Identification, international equipment serial number in the GSM standard, unique for each device
IMSI– International Mobile Subscriber Identification, the international serial number of a subscriber for GSM standard services, is unique for each subscriber
L.A.C.– Local Area Controller, Local Zone Controller, devices, work manager a certain number of base stations whose antennas serve a certain area.
Local Area– Local zone, an area served by BSs that are part of the same LAC
M.S.C.- Mobile services Switching Center, Mobile Services Control Center, switch is the central link of the GSM network.
NC– Network Code, Network Code, the code of a specific operator in a given country in the GSM standard (for MTS – 01, BeeLine – 99).
Prepaid– Prepaid, prepayment – a billing system based on instant debiting of funds.
Roaming– Roaming, using the network of another, “guest” operator.
SIM– Subscriber Identification Module, Subscriber Identification Module, SIM card – an electronic unit inserted into the phone on which the subscriber’s IMSI is recorded.
VLR– Visitor Location Register, a register of active subscribers – contains information about all subscribers who are currently using the services of this operator.
Structural scheme GSM cellular phone
The block diagram of a cellular radiotelephone operating in the GSM digital standard (Fig. 5.3) consists of analog and digital parts, which are usually located on separate boards. The analog part includes receiving and transmitting devices, which in their characteristics and construction resemble those described above.
In GSM systems, the transmitter and receiver of a cell phone do not operate simultaneously. Transmission occurs only for 1/8 of the frame duration. This significantly reduces battery power consumption and increases operating time in both transmit (talk) and receive (standby) modes. In addition, the requirements for the receiver's high-pass filter, made on a SAW, are noticeably reduced, which makes it possible to integrate the LNA with a mixer. The transmit-receive interface unit is an electronic switch that connects the antenna either to the output of the transmitter or to the input of the receiver, since a cell phone never receives and transmits at the same time.
Rice. 5.3. Functional diagram of a radiotelephone digital standard GSM
The received signal, after passing through the input bandpass filter, is amplified by the LNA and goes to the first input of the first mixer. The second input receives a local oscillator signal f direct from the frequency synthesizer. First intermediate frequency signal f etc., passes through a band-pass SAW filter and is amplified by the first intermediate frequency amplifier UPC1, after which it is supplied to the first input of the second mixer. Its second input receives a local oscillator signal f g from the frequency generator. Received second intermediate frequency signal f pr2 is filtered by a band-pass SAW filter, amplified by the amplifier UFC2, demodulated and supplied to an analog-to-digital converter (ADC), where it is converted into a signal necessary for the operation of a digital logic block implemented on the central processor CPU.
In transmission mode, the digital information signal generated in the logical block is supplied to the 1/O generator, where the modulating signal is generated. The latter enters the phase modulator, from which the signal f fm enters the mixer. The second input of the mixer receives a signal f transmitting from a frequency synthesizer. Received signal f c1, through a bandpass filter, enters a power amplifier (PA), controlled by the central processor CPU. Signal amplified to the required level f c1 passes through a bandpass ceramic filter to antenna A and is radiated into the surrounding space.
The digital logical part of a cell phone (Fig. 5.4) ensures the generation and processing of all necessary signals. The core of this important part digital phone is CPU CPU. It is made in the form of VLSI on micropower field effect transistors with a metal-insulator-semiconductor (MDS or MOS) structure.
The digital part of the phone includes:
Digital signal processor (CPU) with its own RAM and permanent memory, which controls the operation of the cell phone. Phone CPUs are somewhat simpler than computer microprocessors, but nevertheless they are complex microelectronic products.
Analog-to-digital converter (ADC), which converts the analog signal from the microphone output into digital form. In this case, all subsequent processing and transmission of the speech signal is carried out in digital form, up to reverse digital-to-analog conversion.
speech encoder, encoding a speech signal that is already in digital form according to certain laws using a compression algorithm to reduce signal redundancy. In this way, the amount of information that needs to be transmitted over a radio communication channel is reduced.
Channel encoder, adding additional (redundant) information to the digital signal received from the output of the speech encoder, designed to protect against errors when transmitting the signal over the communication line. For the same purpose, information is subject to certain repackaging. (interleaving). In addition, the channel encoder includes control information coming from the logical part into the transmitted signal.
channel decoder, separating control information from the input data stream and directing it to the logical block. The received information is checked for errors, which are corrected if possible. For subsequent processing, the received information undergoes reverse repacking in relation to the encoder.
Rice. 5.4. Digital and logical part of a mobile cell phone
speech decoder, restoring the digital speech signal coming to it from the channel decoder, transforming it into a natural form, with its inherent redundancy, but still in digital form. Note that for the combination of an encoder and decoder located in the same integrated circuit package, the name is sometimes used codec(eg speech codec, channel codec).
Digital-to-analog converter (DAC), converts the received speech signal into analog form and supplies this signal to the input of the speaker amplifier.
Equalizer, serving to partially compensate for signal distortion due to multipath propagation. The equalizer is an adaptive filter, adjusted according to the training sequence of symbols included in transmitted information. This block, generally speaking, is not functionally necessary and in some cases may be absent.
Keyboard, which is a dial field with numeric and function keys for dialing the number of the called subscriber, as well as commands that determine the operating mode of the cell phone.
Display, used to display various information provided by the device and operating mode of the station.
Message encryption and decryption block, designed to ensure confidentiality of information transfer.
Speech activity detector(voice activity detector), which turns on the transmitter to emit only during those time intervals when the subscriber is speaking. During a pause in the operation of the transmitter, so-called comfortable noise is additionally introduced into the path. This is done in the interests of economical consumption of power supply energy, as well as reducing the level of interference for other stations.
Terminal devices, used for connection through special adapters using appropriate interfaces, fax machines, modems, etc.
SIM card(SIM - subscriber identification module, literally - subscriber identification module) - a plastic plate with a chip inserted into a special socket of the subscriber device. The SIM card stores:
Data assigned to each subscriber: International Mobile Subscriber Identity (IMSI), Subscriber Authentication Key (Ki) and Access Control Class;
Temporary network data: Temporary Mobile Subscriber Identity (TMSI), Location Area Identifier (LAI), Encryption Key (Ke), Mobile Denied Data;
Service-related data: preferred language of communication, payment notifications and list of declared services.
One of the main purposes of a SIM card is to provide protection against unauthorized use of a cell phone. At the subscriber interface level, a personal identification number (PIN number) of 4 to 8 digits in length is recorded on the SIM card, which the SIM card microprocessor, after turning on the station, checks with the number dialed by the user using the keyboard. If the wrong PIN number is dialed three times in a row, use of the SIM card is blocked until the subscriber enters the 8-digit Personal Unblocking Key (PUK).
If an incorrect PUK is entered 10 times in a row, the use of the SIM card is completely blocked and the subscriber will be forced to contact the network operator.
In addition, thanks to SIM cards, you can make calls not only from your cell phone, but also from any other GSM phone, just insert the SIM card into the device and dial your personal identification PIN number.
5.3 Cellular services. Communication confidentiality. Fraud in cellular communications. Biological safety.
In second generation systems, the user can be provided with basic and additional communication services. Basic communication services: telephone communications, emergency calls, transmission short messages, fax. The emergency call service allows you to set subscriber station voice communication with the nearest emergency service center. Additional communication services include:
· number recognition services;
· call forwarding and forwarding;
· call termination services (call on hold, call on hold, etc.);
· conference call;
· services for accounting the cost of negotiations;
· group connection services;
· call restriction services, etc.
In conditions of competition for subscribers, operators large networks trying to introduce new services. Recently, services such as subscriber connection on a prepaid basis, WAP service - access to the Internet directly from mobile terminal, system global positioning GPS, video communication, etc. But such opportunities appeared with the advent of communicators (smartphones).
Confidentiality of communication is provided with protection against unauthorized access to communication channels. For this purpose they are used various methods encryption. For example, in the GSM standard, encryption is carried out by noise-resistant coding and interleaving and consists of bitwise addition modulo 2 of the information bit sequence and the pseudo-random bit sequence that forms the basis of the cipher. Reapplying the modulo 2 addition operation with the same pseudorandom sequence to the encrypted information sequence, it restores the original information bit sequence, that is, it implements the decryption of the encrypted message (Fig.).
There is also the possibility of protection against eavesdropping - this is scrambling (mixing, shuffling), which is a kind of encryption by rearranging sections of the spectrum or segments of speech, carried out in external software.
Fig.5.5. The principle of encryption and decryption of information in the GSM standard.
in relation to the mobile phone device with appropriate descrambling at the receiving end.
Fraud(from English fraud- deception, fraud) is one of the serious problems of cellular communications. Fraud can be defined as an illegal activity aimed at using cellular communication services without proper payment or at the expense of paying for these services by people who do not use such services.
From time to time, the world and our press are shocked by reports of fraud in the field of cellular communications. The most unpleasant thing is when a cell phone registered to someone falls into the hands of scammers who are able to deceive cellular providers and carry out large-scale negotiations without control. Sometimes primitive methods are used for this (for example, malicious non-payments), and sometimes very subtle methods based on excellent knowledge of documentation cellular networks communications. They practice altering cell phone numbers and all kinds of “chemistry” with codes and passwords.
Losses from fraud, even after many years of fighting it, reach several percent of the total volume of cellular services. For example, in 1996 in the USA they amounted to just over $1 billion, with total revenue from cellular communications being $21 billion. Most operators try not to publish data on such losses, and they become known to the public years after major “mistakes” .
If you suspect that someone is using (explicitly or indirectly) your device, you must immediately notify your cellular service provider. For example, such a suspicion may be based on a noticeable increase in the volume of payments for cellular services compared to your usual level. If you don't control what happened, you could suddenly receive a bill for hundreds, if not thousands of dollars. And you will be embroiled in a long legal battle with an unclear outcome.
In addition to fraud, the sale of “grey” phones causes enormous damage to cellular communications. These can be rejected devices purchased on the cheap, which are then handicraftally brought to working condition - often without all the functionality. Such devices cause a lot of trouble not only to their owners who are looking for cheap prices, but also to cellular operators. Because, performing many functions poorly (or not performing at all), they cause a flurry of calls to customer service.
Eavesdropping on conversations on cell phones is also far from a harmless thing. Analog networks are especially vulnerable to this. But even in digital networks, even with the appropriate equipment for encoding and decoding conversations, eavesdropping on them is also quite possible. It’s worth remembering this when having conversations.
The methods of illegal use of cell phones are varied, although there is an opinion that you need to be aware of it. But to what extent? For example, it is clear to everyone that a cell phone can be used as a very simple radio fuse. However, a description of even a simple scheme for such an application can hardly be welcomed. The relevant authorities can instantly recognize this as a benefit for terrorists. Therefore, having warned the user about the presence of gaps in the legal use of cell phones, we will end the description of these subtle points in the use of cell phones.
Biological safety.
From time to time, sensational news appears about the development of cancerous tumors from the use of a cell phone. Somewhere in the USA there seemed to be even lawsuits about this. There are also reports of parking lots exploding while cars are being refueled, of planes going astray, of nuclear power plant reactors stopping due to the fault of cell phones, etc. In the vast majority of cases, such “news” is not documented.
In fact, cellular frequencies refer to the type of electromagnetic radiation that is easily absorbed by the tissues of our hands, head and brain. Studies have shown that up to 60% of cell phone radiation energy is absorbed by the tissues of the human head. True, only part of the microwave radiation energy gets deep into the head. Most of it is absorbed by the skin and bones of the skull.
Meanwhile, there is no official data on any effect of cell phone radiation on the human body. And not because the relevant research has not been carried out. But because the standards for radiation power are much lower than the standards that were established for people by the relevant authorities.
Energy absorption rate electromagnetic radiation the human body is the SAR (Specific Absorption Rates) value. It is expressed in the energy of absorbed radiation per unit mass (g or kg) of biological tissue. In this case, during 20 minutes of exposure the tissue heats up by 1 °C.
It is not difficult to understand that such a purely “thermodynamic” approach does not at all help to calm people down. For one does not need to have extensive medical knowledge to believe that the effect of radiation is not limited to heating the tissues of the body. It cannot be ignored that at the genetic level, much less powerful radiation can cause disruption of the cellular structure of the body or damage to genes. Therefore, in Europe, for example, the SAR standard is set at 2 mW/g.
By the way, there is a simple way to radically reduce the impact of radio emissions from mobile phones on the human body, and above all on his head. This is the use of a special headset hands free(free hands). This headset consists of a head-mounted earphone and microphone, as well as a radiotelephone control panel. The phone itself can be installed remotely. It is also possible to connect an external antenna to it, which can be installed outside the window or even on the roof of the car.
By the way, of all the types of danger associated with cell phones, the first place is distracting the user from his main job. For example, car accidents are very common when the driver picks up a phone while driving, and especially when he dials a number. In many countries, including Russia, this is prohibited and punishable by fines. Hands free headset and voice control telephone - these are the main means against this factor.
Control questions
1. Name the typical blocks of a subscriber mobile station?
2. Tell us the device and main purpose of analog mobile phone components?
3. Tell us the device and main purpose of digital mobile phone components?
4. Define “fraud” and why is it dangerous?
5. List the main measures aimed at reducing the impact of cellular radiation on the human body?
6. The main symptoms of the disease caused by radio radiation?
7. List the main services provided cellular communication?
8. How is communication confidentiality ensured in mobile networks?