What is a city telephone network?

The city telephone network is a set of telephone exchanges, switching nodes, lines and channels, subscriber devices that provide communication to city subscribers through telephones. In small towns, one telephone exchange is usually located, from which cables are laid in different directions for the operation of telephone sets that are installed at subscribers. The connection occurs through the lines and devices of an automatic telephone exchange (ATS).

In large cities, where there are many telephones, the problem of satisfying the communication of the population, institutions and enterprises of the city with one telephone exchange with a large capacity cannot be solved. In this case, it would be necessary to lay a large number of cables in different directions, and they would be very long. In order for the quality to be good, the diameter of the cores must be increased, that is, this is also an additional cost. The volume and cost of these structures would be very large. This option is economically unsatisfactory.

In order to create urban telephone networks with a large capacity, it is necessary to build several automatic telephone exchanges, which will be located in different parts of the city. Connections between these exchanges will be by means of connecting lines. There may not be many of these lines, and therefore a small amount of cable will also be needed. This would be more cost effective. The energy loss from one apparatus to another will not exceed a certain value. This loss of energy is called damping and is expressed in decibels.

There are several types of automatic telephone exchanges: machine, decade-step, coordinate, quasi-electronic, electronic analog, electronic digital, IP-ATC. Now there is a wide distribution of digital exchanges. They no longer have circuit switching, but packet switching, and everything is transmitted through the IP protocol.