System 12

System 12 , or S12 for short (later also Alcatel S12 ) was the name of a digital switching system that was developed at the end of the 1970s on behalf of the American conglomerate International Telephone & Telegraph .

The original design as "System 1240" originated in 1977 in the United States at the ITT development sites in Connecticut , at the Advanced Technology Center in Stamford and Shelton . After the Bell Telephone Manufacturing Company from Belgium had successfully installed a first productive system in Brecht in August 1982 , the German subsidiary Standard Elektrik Lorenz in Stuttgart delivered a version that was adapted to the requirements of the German Federal Post Office under the name “S12” . The planned introduction in the United States failed at the end of 1985 and ITT sold its telecommunications division to the French Compagnie générale d'électricité (CGE). In 1987, the telecommunications supplier Alcatel emerged from this group . Under her leadership, the name of the system was initially changed in the 1990s to "Alcatel S12", and in a further development it was also marketed as "Alcatel 1000".

In contrast to the EWSD from Siemens and Bosch , the system 12 does not have a coordination processor. Another feature of this switching system is the decentralized route search and the switching of the outward and return route separate from the voice channel.

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  System 12 cabinet general view when open

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  System 12 cabinet connector strips with circuit boards

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  System 12 cabinet slide-in board

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  System 12B printed circuit board

The Alcatel 1000 S12 switches are primarily used in the public switched telephone network ( PSTN ) because analog, ISDN and mobile subscriber devices, private branch exchanges and concentrators can be connected. In addition, the S12 switching systems can be used in packet data networks and special networks (e.g. for rail operators).

In smaller local networks , S12 exchanges are usually used without an actual exchange module (so-called remote peripheral units ). If a subscriber in such a local network calls another subscriber in the same local network, the connection is first switched through to the exchange in the next largest city. This switch is often a long distance switch .

Only then does this long-distance exchange connect and switch back to the local network. The speech path then runs from the local network to the telephone exchange and from there back to the local network. Such local exchanges are in principle just concentrators.

In larger areas, however, S12 local exchanges with their own switching module are also used. This then recognizes whether the caller wants to call a subscriber in the local network or in the long-distance network and then switches through either to the telephone exchange or to the selected local network subscriber.

Technically it is related to the "System 12B", which was the basis of many private branch exchanges from ITT / SEL and later Alcatel. The mostly commercially used systems (the B stand for office communication) of the 56xx, Office 2000 or Alcatel 3000 series work with comparable software, but with completely different components than System 12.

Web links

• Picture collection - telephone systems and switching systems including system 12

Individual evidence

1. ↑ Merger plans at CGE and the SEL parent ITT . In the archive of Computerwoche , July 4, 2016, accessed on May 19, 2016