So, we put on a bathrobe, put on shoe covers and a hat, and set off on a journey to the underside of the Chinese economic miracle.

First shift - 8 a.m.

All workers are divided into teams of 10-20 people, they have their own commander, who is a little god in charge of his people. The structure completely copies the army - there are no strong and weak. Achievements are judged solely on how the whole team coped with their work. A certain number of actions for each person is set as a work plan - that is, formally, you can make your thousand details and be free. In practice, the phone assembly line is designed in such a way that the output depends not only on your work, but also on what your comrades do - they give you parts of the phone after their manipulations. This deceptive maneuver serves to increase labor productivity, if the team can mobilize all the workers, then their productivity will increase - but no one will be able to leave the workplace separately.

This is another part of the story that is often forgotten or ignored. In Asia, historically, there are prerequisites for each nation to create classes within - in India, these are the stories of the kshatriyas, as well as the untouchables and others, remembered from the school course, in Japan, the modern caste system of belonging to a particular corporation, company. In China, factories have adopted roughly the same approach, but here the unit of the universe is the work brigade. An individual worker is a cog in a large machine that is not very interested in this machine and should not influence it, his task is only to be part of the whole. An absolutely military approach, in which a particular worker cannot prove himself in any way, is the task of the team - that is, the brigade. It is safe to say that on the social ladder, factory workers are somewhere at the very bottom. Sometimes the brightest, those who can organize the work of other workers, become foremen, sort of sergeants of the working world. What is valued here is not the speed of the work of a particular person, but how quickly the team manages its work. Individuality fades into the background.

A typical working day starts at 8 am. At this time, workers come to the workshops, which are located on several floors, and are built together with the foreman. Each brigade appears at the strictly allotted time - the gap between their output is about 5 minutes, this is done in order not to create a flea market. Therefore, the time of 8 o'clock can be treated as a certain conditional milestone - the factory works around the clock, but on the night shift, if there is no force majeure, the number of workers is less.

Sleep is the most valuable thing the Chinese worker has, and he cherishes it very much - one who does not get enough sleep threatens the well-being of his comrades. The production of the entire brigade may suffer, which means that the working day from 10 hours will turn into 11 hours, or even more. By law, the maximum working day is 10.5 hours. The best crews manage 9.5 hours, but most try to keep it under 10 hours. Gaining half an hour of time is given at the cost of huge efforts, people become squeezed like lemons, they only have the strength to get to bed. Yes, and the factory management can raise output for the Stakhanovites by forcing others to work in the same way. Everyone is well aware of this, so they try to fit into typical norms - only sometimes, due to some festivities, the brigades can speed up.

It is curious that it is customary to celebrate birthdays or other events of workers here. The dining room has separate rooms round tables and the opportunity to seat one brigade. It costs nothing to occupy such a room, the same food is served as for everyone, but people can celebrate something of their own in an intimate setting. It somehow reminds me of army everyday life, where your unit becomes everything for you - exactly the same role for a brigade in a Chinese factory - it should become a home for a worker.

Moving from one team to another is possible, sometimes it happens, but it is not encouraged - it is easier to work with those you know well. The brigadier is not a white hand at all, he works on a par with the rest, although he has some privileges. Curiously, the foreman has to master a greater number of operations in order to train newcomers, if no one else can do it.

The Chinese factory is a sweatshop where workers work hard. In the morning they don't have time for breakfast, so at 11 o'clock there is what is called lunch. In fact, for most workers, this is the first meal of the day. The second meal takes place after 3-4 pm, the ritual of taking workers out of the workshop is repeated.

The foreman leads everyone through a metal detector, and workers can also be inspected on special pedestals in search of parts that they could take out. From the point of view of theft, every factory seeks to protect itself and creates conditions under which it is impossible or extremely difficult to endure anything. At some factories, a paranoid level of secrecy is introduced, when not only players, telephones or something else are prohibited inside the production, but finished products are closed in opaque boxes, which are moved to other workshops.

There is a little secret with which you can determine how serious measures are taken at the factory for the safety of production and what is happening on it. You just need to look at whether the girls behind the assembly line have headphones. The presence of your own players clearly indicates that there is an opportunity to bring something of your own and take it back. As a rule, in most industries this is not possible.

Let's go back to the standard Chinese worker meal. The two meals that take place in the factory are almost all the food a worker consumes during the day. On the territory of the factory there is a small shop with a very modest selection of cookies, sweets and other nonsense to kill the worm. The diet is not rich in variety, and if you look into the dorm room, you will find products such as tea, concentrated juices, soda, cookies and chocolate. Families can cook food, but they do it almost exclusively because of the children who do not eat in the factory canteen.

The scarcity of food ten years ago was fantastic, I'm not sure that this was how they were fed in concentration camps. Some factories amazed me with the lack of not just a balanced diet, it was a cup of rice and some vegetables with tea. This spectacle always impressed the Europeans, but did not touch the Chinese themselves at all - they explained this by the fact that in the villages the food of their workers was even more scarce. There is no reason not to believe these people, I think that it was so. But even then there were no emaciated people at the enterprises, those who gave the impression of being sick or infirm. It is possible that the reason for this lies in the Chinese organization of labor - as soon as the worker ceases to fulfill his norm, he is refused and he is forced to leave the factory. Rough but extremely efficient system, which is focused only on the result. There is no social protection for workers that would allow them to pay money when their work deteriorates. The maximum that a Chinese worker can count on is payments from production if he receives a disability due to the fault of the factory. The amount of such payments is very small and cannot cover the lack of work or provide a decent standard of living.

Another interesting question is the size of the pension in China and why the villagers are so eager to go to the factories. The explanation should be sought in the fact that in China there are no pensions for peasants and rural residents, they do not exist at all. Government officials have pensions prerequisite is a job of at least 15 years. The law also states that in enterprises, including private ones, employees must receive a pension upon reaching a certain length of service. The amount of this pension ranges from 750 to 1200 yuan (3,800-6,000 rubles). As a rule, it is very difficult to fulfill all the conditions for receiving a pension. But this is an additional incentive to link one's life with the factory, since the pension guarantees life in old age. Historically, in China, parents relied on children to support them in their old age - the more children, the better parents lived. The state program "one family - one child" brought a time bomb under this concept, parents of children born since 1980 can no longer count on support - one child is not able to feed two adults. The alternative is to work for the state, which, like a vacuum cleaner, takes away the most gifted and capable children, or, in the absence of education, a trip to the factories. it state regulation an economy that de facto creates and enlarges classes - employees and workers.

Sometimes I stumble upon reports about how Chinese workers live, or discussions of the difficult conditions of their work, as well as life. Some Western publications call it slave labor, which, of course, is not. But the fact that in China the state has created all the conditions for the inhabitants of the country to be employed is beyond doubt. There is a segregation in the country based on the qualities of people, and those who do not want to work have no place in this social structure Most people have to work to provide themselves with food. Much and hard.

The working class in China is not privileged, on the contrary, they are the people on whose shoulders the economic miracle is built, and they are one of its constituent parts. Cheap labor of workers, multiplied by long working hours, gigantic output and low wages, create the economy of this fairy tale.

Conveyor - Japanese version of production

Each factory is fighting for greater production efficiency, this is not about a multiple increase in product yield, but about percentages. Factory managers readily and quickly adapt innovations that occur in production, especially if they are not expensive.

Usually the conveyor on which the phone is assembled is a straight line with assembly tables. On each such table, a certain operation is performed - first a board is inserted, then other parts are mounted, and so on. At the end of the conveyor, there is a primary inspection of the resulting product or semi-finished product, at certain stages there is a quality check (both instrumental and by the eyes). In Europe, in such factories, you can see chairs, and low tables, adapted for seated people. In Asia, all production, or almost all, is for standing people (imagine 10 hours on your feet, in almost the same position and at a narrow table? This explains the fatigue of people after a shift). The choice in favor of people standing during production is explained by physiology - pressure does not drop, concentration on details is higher and longer. The payoff for this is more rest time, sleep. For factories, this is beneficial in that workers do not have time for walks or anything else, they either sleep or work.

At the Oppo factory, a slightly different type of conveyor was used, it was not put in one line, but with the letter P. This innovation was applied in Japan about a year ago, as they say, this option saves space and speeds up work by the same percentages. Workers stand on the inside of the letter P and pass blanks to each other.

The Oppo factory employs 1,700 people on a day shift and has 40 production lines that assemble phones. The plant is capable of producing up to 50,000 devices per day, but the actual production volume is slightly less, it is regulated night shift, which is not so numerous.

The conveyors described above are typical for any plant, whether it is located in China or another corner of the world. In fact, we can say that most of the devices are assembled by hand, and this applies equally to both Oppo phones and the Apple iPhone coming out of Foxconn factories. share manual labor in each apparatus remains the maximum, and the idea of ​​\u200b\u200bthat all this is assembled by robots is as far from the truth as the number of such industries (they exist, but almost never produce goods for the mass market, the cost is too high, it is cheaper to use workers arms).

Full-cycle production also has its own SMT lines, where telephone boards are assembled. Almost always, when they want to talk about the fact that the production is modern and innovative, they show an SMT line as a picture, on which machines lined up in a row string small parts onto a board, picking them up from reels. Robots skillfully and quickly collect boards, which then pass primary control quality.

The cost of one SMT line for the production of telephone circuit boards is about 10-12 million dollars. There are five such lines at the Oppo factory, and it is planned to purchase two new ones with improved equipment. In fact, for each production, the maximum output depends not only on the number of workers and assembly lines, but on the number of SMT lines. Usually the ratio is 1 to 5, that is, five conveyors with workers are opened per SMT line. This clearly shows the difference in the productivity of machines and humans.

The economy of production and conveyors is approximately the same for all companies, that is, here we can say that the equipment differs, the cost work force and the thoroughness of intermediate testing at all stages of assembly. But the main difference in price between different factories lies in other aspects of the work, we will talk about them.

Testing of components and finished products

If an experienced eye can see a lot of things in the workshops, evaluate the quality of the organization of work, roughly estimate the cost of the product, then it will not be able to identify the main thing - how good or bad the final product is. Quality control is responsible for this, and it is by no means concentrated in industrial premises is a separate laboratory. In factories where quality is paramount, there are two laboratories - one is engaged in testing their own, finished product, and the second checks all purchased components plus considers components from new suppliers. In the case of Oppo, there are both labs. There were models on the test benches that have not yet been officially announced, so I won’t be able to show you all the devices and test machines. But in in general terms I'll tell you what happens behind the walls of these rooms. Let's start with the component testing laboratory.

Each factory independently purchases a variety of components - from plastic and screws to stickers on phone screens, displays, material for printed circuit boards. Two hundred items are required to assemble one phone, and the work and quality of the final product can directly depend on any of the components. Therefore, input quality control is very important, and it starts with the simplest tests - the weight and size of the components. The supplier has specifications according to which he produces, for example, screws. They must be of a certain size, weight and color. All this is checked for each batch that is delivered to the factory - this is where random checks take place. If the supplier is new or the component has never been delivered before, then the test is carried out on all possible machines - resistance to aggressive environments, humidity, strength characteristics, and so on. Whether or not a component passes these tests determines whether the factory will buy it or not. Often components of several companies are tested simultaneously and the best ones are selected.

In the photo below, you can see how the laboratory checks the oleophobic coating of the display by a drop of liquid placed on it.

This laboratory has X-ray machines to detect hidden defects in small parts, circuit boards, and so on. That is, it is a full-fledged quality control of all components. Exactly the same way accessories are checked, for example, headphones. After testing, they are cut so that by mistake they do not get into the manufactured products; weighty bags with cut off ears and connectors can be found in different places.

There is a separate room with test charts for cameras, where modules are tested - even before they are installed in phones, you can also check the final devices and how the software works.

The laboratory looks worn, it is not brand new, which better than any words says that life is in full swing in it and work is constantly going on. This is one of the most interesting places in the factory. As a rule, outsiders are not allowed into these laboratories, since the equipment does not make a stunning impression, moreover, it is very difficult to explain its deterioration, and such explanations can be taken as excuses.

Several times I was not lucky enough to get on press tours of factories, where we were taken to specially created production facilities, in particular, we were shown perfectly clean laboratories of input quality. When I asked how long ago the laboratory was built, I found the answers very funny - a year ago, several years. Such laboratories cannot always be tidy - they are clean, but equipment wear and scratches occur due to the fact that they are used. But if they do not use it, then there is nothing.

In the test lab where finished phones are tested, there are several rooms, each of them is designed to test devices in different conditions. I'll start with the climatic laboratory, which has large metal cabinets - inside each such cabinet a certain temperature and humidity can be created, this is an imitation of different climatic zones.

Phones can be inside both on and off. A separate installation is responsible for the artificial aging of materials; this is, perhaps, the place where they try to get away as quickly as they do not want to give out their know-how. By and large, an aging plant is a combination of machines that simulate climatic conditions - usually ultraviolet is added to humidity and temperature, and possibly something else. It is the testing methodology that is the secret - it is important to achieve a real aging effect in the shortest possible time. short term, which allows you to change technological process and avoid problems in the future. European engineers regard such installations as shamanism and condemn them, quite sensibly noting that they are not certified, they are a product tied exclusively to Chinese realities and do not have a 100% guaranteed result. There is no harm from them, but a certain benefit can still be traced. I wouldn't be surprised if the Chinese eventually come up with something through trial and error that works and guarantees results. So far, this direction can be perceived as promising, but by no means the main one.

For IP/IPX phones, there are cameras in which the devices are filled with water at different angles (the most interesting thing about such cameras is the wipers that clean the glass of water from the inside so that you can see the device).

Domestic use and durability of the devices are tested on other devices. The mechanical strength of the screen is tested by metal balls that fall on it from a certain height. I didn’t dare to put my phone under this torture machine, although I understood that it passed exactly the same tests and must withstand everything here. Psychologically, this is the most win-win test that the manufacturer can show - a heavy metal ball falls on the screen and leaves no traces on it.

An automatic machine works on abrasion of the surface with jeans put on the handles, a phone in the pocket, and the fabric rubs against the body. Approximately several hundred thousand times. In general, when I talk about strength or abrasion tests, you need to understand that they go through 100-300 thousand repetitions. This is an automatic machine that checks the number of clicks on the screen in different places, and a device that photographs a magazine page, immediately erases the picture and takes pictures again - this is how the camera resource is checked.

In another machine, the phone is clamped in two legs, and they begin to twist it in different directions, trying to bend it. Nearby, the device grinds the surface of the plastic with different materials - fabric, denim, leather and others. It is also a surface abrasion test under different conditions.

Measured pops are heard from another row, about ten phones are lifted 10 centimeters on suction cups and then dropped onto the metal surface of the machine. Then the suction cups fall again, and everything repeats. This happens a hundred thousand times, and the phone must pass all the tests.

Separately, there is a radio laboratory, where they check how the radio module of the phone works. An artificial hand worth 2,500 euros holds the phone, and inside a sealed chamber, all frequencies are tested. There are two such cameras at the Oppo factory, the nameless ones have Chinese manufacturers or there are no small factories at all, it is too expensive.

A short afterword, or to be continued

If in the first part of the report from China we talked about the place of factories in the state, what they are like, how propaganda works in production, then in this part we were able to look behind the scenes of production and see production shops, as well as laboratories on the example of one, pretty good factory. Behind the scenes, there was a story about the highest paid employees of the factory, the role of design and why there are so many different shells for Android and what kind of human factories are doing this in China. This will be the subject of the third part of the report. Don't miss it. I also hope that after this material the question of why one device costs one hundred dollars and the other three hundred, and whether this is only a payment for the brand, will not arise. This report shows what affects the cost of the final product and what such thorough testing brings, in addition to increasing the price.

Russian manufacturers of communication equipment, network, fiber optic, telecommunication equipment. Major brands and new brands. Catalog 2019, official websites, addresses, contacts and prices of manufacturers. Product Suppliers own production- reliable partners. Become a dealer, order a price list!

Manufacturers of communication equipment and telephone equipment in Russia cannot yet compete equally with foreign ones, although the products are much better adapted to the Russian cable infrastructure.

A significant amount of the market is occupied by fiber-optic networks. For 2013 The production of optical cables has increased from 7110 thousand km. up to 8366 thousand km. Russian factories modern equipment communications develop, manufacture, implement and maintain products independently.

Among the first - CJSC NPK POTEK, specializing in the creation and implementation of multi-service geographically distributed communication networks and television and radio broadcasting. The plant manufactures over 50 models of equipment and occupies a leading position in Russia and neighboring countries.

Zelax is a Russian developer and manufacturer, has been cooperating with largest enterprises strategic sectors of the Russian economy and government agencies. Russian customers of Zelax, for whom the reliability of equipment is paramount: the Federal Security Service, the Ministry of Internal Affairs, the Ministry of Emergency Situations, the Ministry of Defense, the FSO, Gazprom, Russian Railways, Rostelecom, AvtoVAZ. Products are certified and comply with GOST.

For 14 years he has been working with telecommunications in Russia and the CIS countries "First Russian Telephone Company" from idea to implementation, implementing independently. The company develops and produces solutions for communications and telecommunications, which is used in Ukraine, Kyrgyzstan, Kazakhstan, Armenia.

Broadband radio access systems are another market area where Russian developers have been successful: 60% of wireless networks in the country use routers Russian manufacturer InfiNet Wireless.

If you are interested in the products of manufacturers presented in the catalog, you can contact the factory directly using the contacts indicated, become a dealer or wholesale partner in your city.

The Kaluga plant of telegraph equipment (part of the Roselectronics holding) today is one of the modern developing enterprises with high technical and technological capabilities, capable of producing both single products of any complexity, and mass production up to 1.5 million products per year.

The modern products of the plant - a new generation of communications equipment, mobile hardware communications and command and control vehicles for the defense departments and the Ministry of Emergency Situations, telemetry equipment, automotive electronics, telecommunications cabinets and racks, are different high quality and reliability.

Application progressive technologies and the most modern imported equipment can significantly increase labor productivity, quality, reliability, raise the technical level, shorten production preparation time as much as possible and, ultimately, increase the competitiveness of manufactured products.

Particular attention is paid to the implementation of special means communications of a new generation: complexes technical means alerts P-166M, hardware documentary communication and KShM, color facsimile machines P-112.

1. Hardware special documentary communication K-8M. It is intended for organizing communication at field mobile communication centers of control points. The transport base of the control room is made on the basis of a K5350 van body on the chassis of a KAMAZ-5350 vehicle, which allows it to be used in the field, without being tied to the road network. The control room consists of two compartments: a compartment for the chief and mechanic of the equipment and a compartment for documentary communication operators - 4 workplaces.

The company is installing automated system control of the parachute battalion of the airborne division on the basis of a unified command vehicle (BMD-2K). The system is designed to control units of the battalion control level of the airborne division in various conditions of the operational-tactical situation and provides a solution to the tasks of automating the main control processes, information and calculation tasks and information exchange.

2. Block of the device for collecting paratroopers (BUSD).

3.

BUSD provides:
- transmission of commands to the R-168-K-0.5MKM radio station for switching to the ZCH channels and temporary channels;
- exchange with the R-168-K-0.5MKM radio station of transmitted and received formalized messages;
- power supply to the radio station;
- exchange of formalized messages with automated mobile unit (AMU) workstation;
- determination of the geographical coordinates of the APE according to the data of space navigation satellites and their transfer to the subscribers of the complex of control means of the paratrooper and to the automated workplace of the APE;
- input and storage of setting parameters from AWP.

4. The display and control unit (DCU) is part of the paratrooper collection device and is designed to work as part of a paratrooper’s wearable control system, allows you to navigate the terrain without a map, because as the user moves towards the target, the coordinates of which are entered in the memory of the BOU, the distance to the target and the direction to it are corrected.

5. The enterprise also produces facsimile machines for the needs of the Armed Forces of the Russian Federation. The P-112 fax machine combines the functions of a system printer, scanner and fax and is designed to transmit, receive and document color graphics and text information in communication and data transmission systems of the Armed Forces of the Russian Federation, as well as via the public switched telephone network. It is intended for installation on stationary and mobile objects.

6. JSC "KZTA" has a powerful production base necessary for the production of electronic and electromechanical components and products.

7. Mechano-preparation production (high-precision machining on automatic lathes, machining centers and CNC machines).

8. laser cutting metals and forming the necessary parts on high-performance CNC pressing equipment, which allows you to minimize the time required for production preparation.

9.

10. Tool production has a wide range of high-precision equipment from leading domestic and foreign companies (MAZAK, Sodik), which is able to fully meet the needs of the organization in stamps, molds, molds, cutting and measuring tools in the shortest possible time.

11.

12. Assembly and assembly production (including the installation of surface-mounted radio elements) using an automatic machine screen printing, an automatic PMI installation, a convection melting oven and an automatic optical inspection system, a sealing area for printed circuit assemblies using an automated line for the selective application of moisture-proof coatings with visual quality control of the application.

13.

14.

The enterprise pays special attention to supporting young specialists, a career planning system is in place for promising employees, and many employees of the plant have been awarded departmental and state awards.

Today, the plant is developing dynamically, new types of products are being mastered not only for the needs of the Ministry of Defense of the Russian Federation, the Ministry of Emergency Situations of the Russian Federation, but also for civilian use. The technical re-equipment of the enterprise is ongoing. It can be said with confidence that the Kaluga Plant of Telegraph Equipment is a leading enterprise not only on the scale of the Kaluga region, but throughout Russia.

THEME #6

Telephone sets

Lesson #1

Purpose, classification, characteristics and parameters of telephone sets

QUESTIONS:

Appointment and classification of telephone sets.

Main parameters and characteristics of TA.

First study question

Purpose and classification of telephone sets

A telephone set (TA) is designed to transmit and receive called and spoken signals and contains called, spoken and switching devices.

Called devices include devices for making a call and dialing a number (inductor, dialer and call receivers (bells, acoustic signaling devices)).

To conversational devices - a microphone and a telephone, mounted microtelephone handsets, a telephone transformer.

In some types of devices, conversational devices are supplemented by amplifying devices.

A telephone transformer is used to create a conversational circuit of a telephone set, to match its output impedance with the line input impedance, and also to separate the microphone and telephone power circuits.

Switching devices: lever contact switch and in some types of special devices, for example, for operational - technological communication railway transport(buttons and microphone valves).

TA classification:

1) By appointment:

General use, these include conventional TA

Apparatus special purpose, for operational-technological communications (OTS) field, etc.

2) By the way the microphones are powered:

TA of the local battery system (MB);

Central Battery (CB);

Batteryless.

3) By type of station for which they are intended:

Manual exchanges

Automatic telephone exchanges

4) By the method of turning on conversational devices:

TA with a constant scheme for switching on conversational devices (Fig. 6.1.1a), which does not change during the transition from voice transmission to reception and back (public TA used on networks in local telephone communications).

Fig.6.1.1. Schemes for switching on colloquial devices in TA

TA with a variable circuit for switching on conversational devices (Fig. 6.1.1b) characterized by the fact that when transmitting speech, the BM microphone circuit is connected to the device circuit, and when receiving, the BF telephone circuit is connected. These switchings are carried out by the valve (tangent) SP - this is used in operational - technological communication (OTC).

5) According to the method of turning on the call devices, they differ:

a) with the inclusion of calling devices (VP) in the subscriber line L (Fig. 6.1.2a), while the VP are separated from the colloquial devices (PR) by the contacts of the SA lever switch (used for telephone communication of the MB and CB systems).

Fig.6.1.1. Schemes for switching on ringing and colloquial devices in TA

b) with the organization of the EP circuit with the help of the PV call receiver when a call signal is received (it is used in the OTN, as well as in the TA with an acoustic tone call).

6) By the type of calls received gnolov:

With an alternating current call with a frequency of 25-50 Hz. Most common for general use and used in CPU systems

With DC call. Used in MB systems, used in OTS

7) By design:

Stationary (desktop, wall, combined)

portable

Telephone sets can be classified depending on their use of one or another type of communication (Fig. 6.1.3).

Fig.6.1.3. TA classification by types of communication used

The circuit-switched network predominantly uses the simplest analog telephones, in which voice signals are received and transmitted in analog form. ISDN digital telephones, which receive and transmit digital voice signals, also find use on such networks. In packet-switched networks, users have IP phones installed, which also provide information transfer to digital form. The considered devices are characterized by the fact that they are installed in the place where the subscriber line ends. In mobile networks, telephones can change location within the network and can be used on the move. This became possible due to the fact that instead of a wired subscriber line, a radio channel appeared here.

In the telephone set, it is necessary to supply power from a DC source to various devices: a microphone, amplifiers, microcircuits. Telephone sets can be powered by a central battery system (CB) or local battery (MB).

In the power supply system of the Central Bank, telephone sets are powered from a common source located at the telephone exchange and called the central battery. At the PBX, the common DC source has a voltage of 48 V ( foreign standard) or 60 V (Russian standard). In a centrally powered system, the supply voltage is also used to make a call from the analog SLT to the PBX. The CPU power system is used for all analog SLTs and for most ISDN digital SLTs. In a packet switched network, IP phones can also be powered by the network node in which they are connected.