City telephony cannot do without such an important element as a communication center. It is a whole range of technical means that are used by the telecom operator to provide high-quality communication services. We are talking about various services (PBX, WEB, etc.), as well as routers necessary to ensure connection with the provider.
From a physical point of view, the node is placed in a large rack, and routers and servers are also installed in it. For its placement, a separate room is usually chosen, it is maintained at the optimum temperature for work, and specialists with insufficient qualifications are not allowed there. As a rule, such a structure should be placed in a building located in the central part of the city. In the same house, most often there are those institutions that need a stable connection, but do not have their own telephone exchange, we are talking about public points for accessing the Internet, post offices, and telegraphs.
Background: 19th century
Appearancethe first communication nodes should be attributed to the end of the 19th century, it was then that the American scientist Alexander Bell invented the telephone. Already in 1877, active production of telephones with two handsets began, which were connected to each other with wires and were located in the same room or house. At first, this system was very popular, but soon there was an urgent need to connect several lovers of conversation at once.
It was then that switchboards were created, which were controlled by hand. The owner of the device picked up the phone, then twisted the handle, after which his call immediately fell on the operator on duty, then they were mostly girls. The telephone operator had to announce the name of the person with whom the subscriber wanted to talk, and then she connected the two parts of the cable together in order for the conversation to take place.
Background: 20th century
By the beginning of the 20th century, regional communication centers appeared, in which 40-50 telephone operators worked at the same time, they had to connect all incoming subscribers around the clock. The work was quite time-consuming and resource-intensive, so soon the question arose again of how to translate it all into an automatic way.
Only by the beginning of the 1920s, inventors managed to achieve the possibility of a direct connection between two subscribers. It was then that telephones began to embed disks with numbers that were used to dial a number. The equipment providing communication between subscribers has also been subjected to seriousmodernization, if at the beginning of the 20th century it could occupy an entire floor, now a five-meter room is enough to accommodate it.
Knots today
The telephone communication center today is a whole range of automatic stations that are able to provide a connection between two subscribers without the participation of additional human resources. At the same time, it must be universal and be able to communicate not only with subscribers who are connected only to it, but also with others who are served by other telephone exchanges.
A well-built PBX structure is capable of supporting the connection process between devices for a long time, as well as providing a number of additional features. This effect is achieved through the use of telephone signaling, as well as continuous improvement of the system.
How do node components work?
Large cities are mainly served by regional communication centers, which should have a large number of functions. First of all, it is a question of the equipment at the site recognizing the ringing signal from the system user who needs outgoing communication. The subscriber hears a continuous beep, which is a signal that the system is ready to receive information for further actions. As soon as the user dials the number he needs, the system must remember it.
Next, the dialed combination is searched, while all the elements of the number that are involved in it are temporarilyare marked and become busy. This is necessary so that no one else can talk to this number at the same time. In the event that the elements (or paths) of the number are busy, then the calling subscriber will hear the corresponding signal in the form of frequent beeps. In this case, you will need to try again later.
How is getting connected?
The elements of the communication node are aimed at connecting the selected communication channel as soon as possible. That is why they are used to inform the called subscriber about the incoming call. At the same moment, the client of the system who decided to use the outgoing connection receives a tone signal informing him of the call attempt. This dial tone is repeated at 4 second intervals if the called user does not pick up the phone.
As soon as the call from the other side is accepted, the system automatically connects both users to the path and provides the opportunity to talk. Here it is necessary to take into account a number of limitations, in particular, the fact that the nodes serve not only fixed telephony, but also mobile phones. The latter may have a call duration limit of 30 minutes, please check with the operator for details.
As soon as the dialogue has been completed, the communication node receives a corresponding signal to terminate it. Further, the process occurs in the reverse order - all elements used in the construction of the communication path are disconnected, the marking of the number components is turned off. This is how it is donetelephone connection between two subscribers, with the advent of conference calls, their number can increase to five or more.
Knot types: USSR
The very first communication centers consisted of machine automatic telephone exchanges, which were a large machine drive from a large number of shafts. Their design was such that a particularly stubborn subscriber could connect to a number in a very congested direction, while he did not have to call back, but just had to hold the phone to his ear for a long time and wait.
After the Great Patriotic War, they began to be replaced by ten-step stations with complex electromechanical devices. When using them, a significant drawback was revealed - a large amount of interference, so they were soon replaced with coordinate ones. The latter began to use markers and registers, greatly simplifying the process of remembering the number and connecting between subscribers.
Knot types: Russia
After the collapse of the USSR, quasi-electronic stations began to appear, which had improved communication quality, some of them are still working. Electronic telephone exchanges, which are divided into analog and digital, are very popular today. The former are used at small nodes with a small number of subscribers and have very low immunity from interference.
Digital ones, which are installed at most urban communication centers, completely translate the signal into the desired format andtransfer it to each other almost in its original form. Due to this, it is possible to reduce the amount of interference, as well as to avoid signal attenuation during the dialogue. Not so long ago, IP-telephony began to become widespread, where it is customary to use packet switching, due to this, telephone exchanges appeared, which were called IP-PBX.
How is the post office?
Post communication nodes are organized according to a similar principle, messages are received and transmitted using modems that are on the same network as the computers of the organization's employees, this system is called "Telex". For data transfer, it is customary to use it, as well as e-mail. The wired telegraph network in Russia practically no longer exists, its active dismantling began in the early 2000s and continues to this day.
In European countries, the telegraph has long been called obsolete and ceased to service it. It stopped working in Holland in 2006, in India in 2013, and in 2017 Belgium also abandoned it. Some US postal operators also refused to use this type of communication, however, in Japan, Germany, Sweden, Canada and other countries, the telegraph regularly performs the function assigned to it.
How to organize this node: room
If you own your own telephone exchange, organizing a communication center is the very first thing you need to do. You need to start by choosing the right room to place it, it does not have to be large, the main thing is that the floor must withstand the load that you have planned. Postcabinets, racks and racks so that they do not interfere with each other and their parts do not touch. Be sure to install an air conditioning system and its backup to avoid overheating of the PBX and their failure.
Above the room there should not be communications through which water passes, and the floors in it must be made fireproof. If there are windows in the future node, they need to be tinted or covered with plywood, since sunlight on the equipment is undesirable. The room should have good lighting, all metal structures must be grounded and additionally fenced off with materials that do not conduct current. It is also recommended to place dielectric rubber carpets, carbon dioxide type fire extinguishers and a first aid kit indoors.
How to organize a communication node: racks and cabinets
What is required for further work? The scheme of communication nodes that will be located in the room should be as convenient and understandable as possible not only to you as a person who constantly works with electrical equipment, but also to a completely outside visitor. That is why it is best to take care of placing all stations and servers in racks and cabinets in advance. Try not to use cabinets that are too tall, as they may not support the weight of the equipment and fall over. If there is not enough space to fit multiple racks and you have to install all the equipment in one, then it is better to additionally fix the shelves.
Inside each cabinet or rackvertical organizers should be installed, with their help it will be much easier to bring optics and power to the equipment. You can assemble the equipment with your own hands, if necessary, you can purchase it in a store, order delivery and assembly, so as not to waste your time. Remember that racks and cabinets with telephone exchanges and servers should be located at a remote distance from windows and air conditioning systems.
It doesn't matter what exactly you are building: a regional communications center or a city one, in any case, you must immediately create reserve capacities. In the event that one of the nodes becomes unusable, you can immediately transfer the load to the backup. Particular attention should be paid to the fact that only those who have the appropriate permission can have access to the premises you built, this is a mandatory requirement of the Ministry of Information Communication.
Conclusion
If you are a small operator providing communication services to a limited number of subscribers, you can register your equipment using a simplified scheme. Now it is not necessary to create documentation for absolutely all systems of your station, which is very convenient - one photo of the communication center is enough to build it. However, all requirements must be met, since technical supervision can come to you with an audit at any time.
Follow simple safety rules when creating a node, this is guaranteed to save you from trouble and accidents. Your room must be airtight; to clean it, you will need to purchase a vacuum cleaner, a dampthere will be no cleaning. Be sure to sign all elements of the site, hang signs on cabinets and racks, post an evacuation map so that all employees know what to do in case of danger.
