As a landline, even PSTN (English Public Switched Telephone Network), the ensemble of all public wireline telephone networks is called. Under wired is understood to end users especially the last mile, so the connection. Public networks, as part of the fixed network, can be publicly or privately owned, but are of the general public either regional ( eg Netcologne ) or widely available (eg the telephone network of Deutsche Telekom ), and are subject to the German-speaking the requirements of the federal telecommunications Act.

Non-public wireline telephone networks with their own numbering plans, in Germany for example, the telephone networks of the Bundeswehr or the Deutsche Bahn AG, are not part of the fixed network.

  • 3.1 Germany
  • 3.2 lines
  • 5.1 Overhead Line
  • 5.2 Twisted copper wires
  • 5.3 coaxial Cable
  • 5.4 carrier frequency system (PLC)
  • 5.5 Fiber Optic


The fixed network is divided into the core network and the access network.

Core network

The core network connects the individual switching nodes with each other. The physical basis is twisted copper wires ( twice or four times), coaxial cable, microwave radio and fiber optics. There are here several channels by multiplexing combined into one large. In the " almost - synchronous transmission " of the plesiochronous digital hierarchy (PDH ) Data transfer rates are up to 564 992 Mbit / s. The modern SDH technology ( Synchronous Digital Hierarchy ) achieved data rates in the Gbit / s range. The PDH technology is therefore displaced by the SDH technology and used for new installations only in the access network.

Access network

The access network connects the end user with the switching nodes (see last mile).


The beginning of the communication networks were manual switches that were star-shaped and connected to each other by the " Lady of the office." From the beginning of the 20th century, this manual switchboard was gradually replaced by electromechanical switching elements, but the hierarchical structure maintained. At that time, formed in Germany seven central offices the top level of the network, which each had its own identification number. This level was finely divided into three further steps. A phone number built through this outline from - to and the subscriber number - - - - . This resulted in up to five-digit codes that are still used today in the German landline. With an increasing volume of calls between two offices, however, cross-links had to be installed so that the strict hierarchy was ever resolved. The power developed in an incomplete mesh. Meanwhile, the electromechanical switching elements are completely replaced by large scale integrated circuits, the so-called switching networks and their control. The network is divided today into two levels:

  • Local level VE: O ( switching unit site) and
  • Remote level VE: F ( remote switching unit ).

There are also foreign exchange ( unit: A).



In Germany, there are 37.98 million fixed lines (as of 2011 ), make phone calls using the 191.2 billion minutes a year (as of 2011 ). Furthermore, there are 26.9 million DSL broadband connections (July 2011 version) with an average data volume of 11.6 GB per month (as of 2011 ).


The CIA reported that in 2003 approximately 844 million routes for landline connections exist throughout the world.

The People's Republic of China has handled most of to 263 million, second only to the United States with 181.6 million fixed-network lines. In comparison, there are in the United States 158.7 million mobile phones.

Everywhere in the world it is expected that in a few years the number of mobile subscribers will surpass the number of subscriber lines. According to an estimate by the Federal Network Agency telephoned in 2011, every German average of 60 hours, including 39 hours via landline. The number of call minutes from mobile increased from 2009 to 2010 by 10 percent. 2011 decreased the number of calling minutes on a landline by 2 percent to 191 billion.

Demarcation to Mobile

From landlines, a distinction the wireless network, consisting of the PLMN and the access network, the connection to the end user, which is done wirelessly via the so-called air interface.

The distinction between fixed and wireless networks is mainly for the last mile, are directed at the phone calls to a fixed local loop. Here the infrastructure is mostly designed as underground cables with copper pair. For several years, fiber optic cables are used. About the cables of the subscriber lines and other services can be enabled in addition to the analog telephony, including ISDN and DSL. The DSL technology is limited to copper cables.

Only in the military field, the core network is regularly built with mobile joints.

Details about the types of lines in the fixed network

Overhead line

  • Possible frequencies: 0 Hz -100 kHz
  • Repeater distance: 2-20 km
  • Bandwidth: <10 kHz
  • Bit error?
  • Examples: above-ground telephone line, obsolete, used in Germany mainly in the ground internal telephone network

Twisted copper wires

  • Possible frequencies: 0 Hz to 750 MHz
  • Repeater spacing: 1.2 km
  • Range: 100-600 kHz
  • Bit error about 10-5
  • Details of ADSL over copper pairs are regulated by Directive G.992.1.
  • Examples: telephone network ( local loop ), Ethernet

Coaxial cable

  • Possible frequencies: up to 5 GHz
  • Repeater distance: 1-10 km
  • Bandwidth: 900 MHz
  • Bit error about 10-7
  • Examples: telephone network ( internal network ), Ethernet, cable TV, antenna cable

Carrier frequency system (PLC)

  • Possible frequencies: 30 MHz ( over long distances up to 500 kHz )
  • Repeater spacing: up to 200 km (depending on system )
  • Bandwidth: up to 20 MHz, for large distances <10 kHz
  • Bit error?
  • Examples: Cable radio, messaging on high-voltage lines (carrier frequencies around 1 kHz and between 30 kHz and 500 kHz), PLC Connection for PC

PLC systems are an intermediate form of wired and wireless communication, there can be received with PLC systems transmitted signals in the vicinity of the lines with radio receivers for the corresponding frequencies. This has been exploited previously in Norway at the so-called Linjesendern. These were broadcasters in the long wave range, took the power lines for transmission. PLC systems should be applied only when it is ensured by the choice of transmission frequency that no radio services in the long - and short- wave region to be disturbed.

PLC is also called to network computer or a method ( called in-house Communication in operation within a house) to the Internet to connect. The operation caused on the domestic or public power lines interference in the shortwave range. Weak shortwave transmitters are interfering with a strong noise or staccato noise that can be heard in neighboring houses or apartments. In this case, the Federal Network Agency prohibit the operation of these devices.

Fiber Optic

  • Wavelengths used: 850 nm, 1300 nm, 1310 nm, 1550 nm or 1625 nm
  • Repeater spacing: 10-100 km
  • Data rate ( for each channel, that is, wavelength): up to 40 Gbit / s, in the lab 160 Gbit / s
  • Examples: telephone network ( local loop ), FDDI