History of the telephone network

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From laboratory experiments to the telephone network

The invention of the telephone

Several people were involved in the development of the first telephone set.

As early as 1844 Innocenzo Manzetti postulated the idea of ​​building a telegraph and in 1864/65 built an electrical device that could transmit the human voice over half a kilometer. The German Philipp Reis played an important role with his construction from 1861. Reis invented the term telephone for this . The decisive factor for the practical introduction of telephones, however, was that in 1876 Alexander Graham Bell managed to beat his competitors Elisha Gray and Antonio Meucci with a successful patent application and , on this basis, legal hurdles for them, and later also Thomas Alva Edison , to launch their own telephones on the market to put in the way. On June 11, 2002, Antonio Meucci was posthumously awarded the patent for the invention of the telephone set by the House of Representatives of the United States Congress.

First telephone company set up in the USA

In July 1877, Bell, who had obtained the American patent for rights to a telephone, founded the Bell Telephone Company together with Thomas Sanders and Gardiner G. Hubbard, including his assistant Thomas Watson. Two days later Bell married the daughter Mabel of his business partner Hubbard. Because of sales difficulties, Bell and his companies offered the patents of the powerful Western Union Telegraph Company - Elisha Gray's employers - for $ 100,000. The Western Union refused - which they would soon regret bitterly.

Still, America's telegraph companies foresaw that Bell's phone would pose a threat to their business, and they tried to counter it. The Western Union Company had Thomas Alva Edison develop their own telephone with different technology. Bell then sued Western Union for infringing its patent rights. She tried to argue that Elisha Gray actually invented the phone, but lost the case.

In March 1879 the Bell Telephone Company merged with the New England Telephone Company to form the National Bell Telephone Company, of which William H. Forbes, son-in-law of Ralph Waldo Emerson , was president . In April 1880 there was another merger with the American Speaking Telephone Company to form the American Bell Telephone Company.

In 1885, the American Telephone and Telegraph Company (AT&T) was founded to conquer long-distance lines across the United States for the Bell system. Theodore Vail became the company's first president.

In 1925, the Bell Telephone Laboratories were set up to combine the research laboratories of AT&T and the Western Electric Company. AT&T subsequently became the most powerful telecommunications company in the world.

First development steps in Germany

Inscription on a house facade from 1909
Pattern from the Rhineland Cable

In Germany , there have been no further efforts to develop a telephone for practical use since Philipp Reis' laboratory experiments . It was not until 1877, when the Bell Telephone Company had started selling the Bell telephone, that the Berlin postmaster general Heinrich von Stephan carried out experiments with two Bell telephones from October 1877 to April 1878. He set up a two-kilometer telephone connection that began testing on October 25, 1877 . In order to create the basis for further experiments, the company Siemens & Halske was commissioned to manufacture further devices. Since the Bell telephones did not yet have a wake-up device, the telephone could only be used as a product with the Siemens signal whistle, which was invented at that time. On November 12, 1877, a telegraph office in Friedrichsberg near Berlin went into operation. From November 1877, Siemens & Halske produced 200 telephones a day, most of which were soon sold to private households.

From 1881 the telephone networks were set up. The placement was done manually, initially only by men. But it quickly became clear that the higher frequencies of a woman's voice with poor line quality were easier to understand than the lower male voices - the lady from the office was invented. The first local networks were opened in Berlin , Breslau , Frankfurt am Main , Hamburg , Cologne , Mannheim and Munich .

Telephone exchange in the army of the German Reich

Telephone lines were also laid between larger cities from 1883. The telephone line between Bremen and Bremerhaven was the longest telephone line in Germany when it went into operation on October 15, 1883. In 1884 the telephone lines followed from Cologne to Düsseldorf and Bonn . In 1885 the local telephone networks of Frankfurt, Heidelberg , Mainz , Mannheim and Wiesbaden were connected to one another. From Berlin, long-distance calls could soon be made with Hanover (1886), Hamburg (1887), Dresden (1888), Breslau (1889), Frankfurt am Main (1894) and Königsberg (1895). On August 6, 1900, the first telephone line between Berlin and Paris was activated.

In telephony, the connecting cables between the exchanges in long-distance traffic are referred to as long-distance lines. A repeater office was able to amplify the voice and carrier frequency signals and thus compensate for the signal losses on the long-distance lines.

Until 1912, the long-distance lines for telephony were almost exclusively produced via overhead power lines. In 1909, in a harsh winter and extreme weather conditions (icing, snow, storm and hoar frost), rows of masts broke and fell over on the Berlin - Magdeburg pipeline. Despite the greatest efforts and the commitment of many employees, it took months to repair the damage to these lines. This extreme event is considered to be the trigger that plans were developed to continue long-distance traffic through underground long-distance cables.

In 1912, Siemens & Halske received the order to lay the Rhineland cable. This cable was first laid from Berlin to Hanover in 1913/1914.

In 1936 there were 6,647 local networks (25.893 million km of lines) with 3.39 million telephone stations (1.95 million main and 1.35 million secondary lines and 86,000 public telephone stations) in the German Reich.

Development in Austria

After Wiener Privat-Telegraphen-Gesellschaft had received a license from the Imperial and Royal Ministry of Commerce to set up a telephone network, network operations began on December 1, 1881. In the same year the first 154 subscribers were published in newspaper advertisements. In the following year, private companies opened networks in Prague , Graz and Trieste and in 1883 in Lemberg , Chernivtsi and Pilsen .

The new industry developed better than expected, and so the k. & k. Post and telegraph administration , the telephone lines are only telegraphic connections with acoustic devices , in order to integrate them into the state monopoly . In 1887, for example, the first telephone ordinance was issued, no more private concessions were granted and all companies were incorporated into PTV in exchange for replacement by 1895 .

Further technical and organizational development

In order to make the telephone usable, it was necessary to set up a complex system which, in addition to the telephone set, also contained transmission lines and facilities for variable connections. Preliminary keywords for the sequence of development steps:

  • transmission
    • overhead telegraph lines
    • underground cables (from 1936), multiple lines
    • Frequency modulation , multiple use of a line
    • Overseas connections, radio transmitters, undersea cables
  • Services extension
    • Answering machine
    • Facsimile ( fax )
    • Multimedia (cell phone)
  • organization
    • German Reichspost
    • Reichspost / Bundespost monopoly
    • Split into Post and Telecom
    • End of monopoly operation, approval of commercial providers

Development of the self-dialing system

Electromechanical selector based on Almon Strowger's patent

As early as 1879, a patent for an automatic switching device was granted in the USA. But it was not until Almon Strowger's invention, patented in 1891, that it was technically feasible and also commercially successful. The first self -voting exchange with rotary dials ("Strowger voters") was put into operation in La Porte ( Indiana ), USA in 1892 . It had 75 attendees attached and a capacity of 99 attendees. Developments by Strowger and his collaborators Keith and Erickson perfected the Strowger voter . Erickson developed and patented a rotary dial in 1896. This made it possible to connect a dial telephone with a twin wire to the exchange and to control a dialer directly by interrupting the power supply (initially the Strowger system required more lines). The rotary dial (officially called “ number switch ”) was developed by Siemens & Halske and a patent was applied for on April 29, 1913.

The first exchange with dial-up operation in Europe was put into operation in Hildesheim in 1908 and was designed for 900 connections. This made it possible for the participants to vote themselves in the local area. Connections to connections outside the local network still had to be made by hand.

The development of the remote dialing system in Germany began in 1923 with the establishment of the first automatic remote switching center in the Weilheim network in Upper Bavaria. This did not yet include the system of local area codes or area codes according to today's standard. Greece introduced a self-dialing network on February 10, 1930, the system was produced by Siemens & Halske and had prevailed against competing offers from England, France and Italy.

On September 3, 1955, the first self-dialing connection abroad was set up, namely the local connection Lörrach – Basel . Even then, people from Lörrach had to dial the country code 0041 for connections to Switzerland .

The widespread introduction of the self-dialing service dragged on for a long time, probably also due to wars and the economic crisis. The last manually operated local exchange in what was then the Federal Republic of Germany in Uetze near Hanover was not shut down until 1966. The full expansion of the self-dial telecommunications service in West Germany was then achieved in 1972. Hand-switched long-distance calls were still common in a few rural local networks in eastern Germany until the end of the 1980s; the last hand-switched telecommunications office was closed on November 23, 1994 in Potsdam.

At the same time, the railway companies continued to develop their telecommunications network. In this way, an international self-dialing long-distance network was created independently of the public network (in Germany: BASA from 1932).

Development from around 1965

In 1971, for the first time, more telephone calls (11.7 billion) were made in West Germany than letters (11.5 billion) were sent. Until the 1970s, little changed in the technical structure of the devices. When the telephone was part of the basic equipment of almost every household, the desire for new colors and designs arose. Advances in the field of microelectronics made the first touch-sensitive telephones possible in private households in 1975 . From this point onwards, telephones were technically improved at ever shorter intervals, initially with call number memories and display displays , later with electronic ringing tones and hands-free equipment . With ever more powerful electronic components, extensions such as electronic telephone books and user guidance via the display were added. The first cordless telephones were brought onto the market in the mid-1980s .

BIGFON ( broadband integrated fiber optic telecommunications network ) was a system test carried out by the Deutsche Bundespost from 1981 to 1988 in seven cities. The aim was the practical testing of fiber optic technology for all telecommunications services . It was the first technical attempt for an integrated broadband communications network (IBFN), under which a tele -Versuchsnetz ( Video Telephony Network ) to transmit sign language for the deaf was installed.

The digital network

A major technical upheaval in Germany only took place with the introduction of ISDN ( Integrated Services Digital Network ).

In 1979 the Deutsche Bundespost decided to digitize the electromechanical switching technology . The aim of ISDN was to combine the previously distributed services of telephony, fax, telex and other data transmission on one network.

From 1980 to 1987, the plans of the Deutsche Bundespost for the introduction of ISDN were determined on the basis of guidelines and recommendations of the then CCITT (now ITU ). In 1987 the first ISDN pilot project was started in Mannheim and Stuttgart in Germany. ISDN was introduced nationwide in 1989 and has been available nationwide since 1993.

In December 1993, Deutsche Telekom signed the "Memorandum of Understanding on the Implementation of a European ISDN" as one of 26 signatories. This set the course for the introduction of the previously national ISDN ( 1TR6 ) against the system known today as Euro-ISDN ( E-DSS1 ) as the European standard. In May 1994 the necessary software changes in the digital exchanges of Deutsche Telekom were completed.

ISDN was switched off in Germany at the end of 2018. Any remaining ISDN users could switch to All-IP.

The mobile network

A-Netz B-Netz C-Netz D-Netz E-Netz Universal Mobile Telecommunications System Long Term Evolution LTE-Advanced 5G

In 1958, the Deutsche Bundespost , which at that time was also responsible for telecommunications, began building a public mobile network across Germany. Within twelve years it was possible to cover four fifths of the area of ​​the Federal Republic with the radio network . This made the so-called A1 network the largest contiguous cellular network in the world. To relieve areas with high traffic density, the A2 and A3 networks have also been set up. In order to cope with the up to eleven thousand participants, almost six hundred operators were necessary. Therefore, the focus was on changing from manual to automatic switching, which was implemented in 1972 in the B-network . Since this was fully utilized after seven years with thirteen thousand users, the B2 network was added in 1980 and the capacity expanded to almost 27,000 subscribers. In 1986 the C network , which could serve up to 400,000 end users simultaneously, replaced the two predecessors. In addition to portable end devices, which still weighed around seven hundred grams, it was now also possible to connect to mobile phone users whose whereabouts were not known to the caller. After two years of operation, the C-Netz already had over a hundred thousand users. For the end of the nineties, one million subscribers were expected in mobile communications.

In 1992, the D-Netz was the last major innovation in the field of cellular networks in Germany. Compared to the previous networks, there were two main differences: on the one hand, the technical issues were determined by a European commission, so that the way was paved for a uniform European mobile communications solution; on the other hand, the Deutsche Bundespost Telekom (DBPT) agreed to participate for the first time Mannesmann Mobilfunk also allowed a private network operator. Mannesmann set up the D2 network, while the D1 network was set up by the DBPT. The D-Netze were the first German mobile radio networks to be transmitted completely digitally, which not only significantly improved voice quality , but also made small and light end devices possible.

In 1994 the E-Netz was introduced. Except for the frequency range (1800 MHz for E-Netz, 900 MHz for D-Netz) it is technically almost identical to D-Netz; both systems work according to the GSM standard. The E-Netz is therefore not a replacement, but an extension of the D-Netz. In the course of its introduction, prices fell, and thus mobile communications became increasingly attractive to private individuals , so that in 1995 around 3.7 million users were recorded. Within nine years, mobile phone users increased twenty-fold to around 71 million users in 2004.

In 2004 the UMTS network went into commercial operation in Germany . UMTS can be seen as the successor to the GSM standard. It uses frequencies between 1900 and 2170 MHz and, due to better transmission methods, offers a greatly increased bandwidth for data transmission compared to GSM . The nationwide development of the UMTS network is already well advanced in Germany, but cannot be considered complete.

In 2010, the frequencies at the upper end of the UHF television band freed up by the switch to DVB-T were rededicated for mobile communications ( digital dividend ). This so-called 800 MHz band and additional frequencies in the 1800 and 2600 MHz range were used for the new LTE (Long Term Evolution) mobile communications standard from August 2010 . LTE enables broadband mobile internet with a data rate of up to 300 Mbit / s in the downlink and 75 Mbit / s in the uplink, i.e. about seven times more than UMTS. Radiation in the 800 MHz band from poorly shielded cable television networks leads to mutual interference, as the frequency range up to 862 MHz is used here.

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  1. ↑ Look it up! - Facts worth knowing from all areas; Bibliographisches Institut AG, Leipzig; page 372; 1938
  2. ↑ Miss from office has had its day , on berliner-zeitung.de

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