World Library  
Flag as Inappropriate
Email this Article


Article Id: WHEBN0005531172
Reproduction Date:

Title: Ewsd  
Author: World Heritage Encyclopedia
Language: English
Subject: List of Siemens products, Telecommunications in Poland, Telephone Switches, Call waiting, Number One Crossbar Switching System
Collection: Telephone Exchange Equipment
Publisher: World Heritage Encyclopedia


EWSD (Elektronisches Wählsystem Digital in German, Electronic Digital Switching System/Electronic World Switch Digital[1] in English) is one of the most widely installed telephone exchange systems in the world. EWSD can work as a local or tandem switch or combined local/tandem, and for landline or mobile phones. It is manufactured by Siemens AG, who claims that EWSD switches perform switching for over 160 million subscriber lines in more than 100 countries.

DeTeWe bought its first EWSD under license in 1985 for remote switching. Bosch built its first EWSD as a local exchange in 1986. Deutsche Telekom, formerly Deutsche Bundespost, the largest German telephone company, uses EWSD and System 12 (Alcatel), the former more than the latter.

In 2007, Nokia Corporation and Siemens AG formed the new company Nokia Siemens Networks, and responsibility of further development and shipments of the EWSD system is dependent on this new company.


  • History 1
  • Hardware 2
  • Software 3
  • Technical data 4
  • References 5
  • External links 6


EWSD was introduced in 1975 as a successor of the Elektronisches Wählsystem (Analog), which was using analogue technology only.


Main subsystems are:

  • CP (Central Processor)
  • MB (Message Buffer)
  • CCNC (Common Channel Network Control)
  • LINE (Analog Line Group)
  • LTG (Line Trunk Group)
  • DLU (Digital Line Unit)
  • SN (Switching Network)
  • PA (ISDN Primary Access) [2]
  • PDC (Primary Digital Carrier)

All system units are redundant so the inactive side can take over immediately in case of an error.

DLU handles analog and ISDN lines and includes codecs for analog lines, one of the BORSCHT functions for subscriber lines. Digital signals are assigned a time slot. DLU concentrates traffic onto an LTG-B unit, as well as Primary Rate ISDN and V5.2 connections. Supervision and address signaling (dial pulse, DTMF) are also integrated in the DLU. For PCM30 (E-1) connections to other exchanges, LTG-C Units are used, which also handle signaling including SS7, MFC R2 signalling, IKZ (dial pulse), and E&M.

The Switching Network consists of 4 space division stages of 16x16 switches, and a time division section with 16 stages of 4x4 switches. Control is provided by the CP Coordination Processor.

There are the following kinds of Coordination Processors:

  • CP103 with max 22,000 call attempts in the busy hour
  • CP112 with max 60,000 call attempts in the busy hour
  • CP113D with max one million call attempts in the busy hour
  • CP113C with max six million call attempts in the busy hour
  • CP113E with max ten million call attempts in the busy hour


The software of EWSD is called APS (Automatic Program System). The APS is on a hard drive and includes the operating system, developed by Siemens in cooperation with Bosch. It is predominantly written in the CHILL language. Application software is switch specific and serves among other things traffic management, path search, and call charging. Support software serves translating programs, binding modules as well as administration of libraries for generating data. Operating and data communication software serve for co-operation of maintenance centers and switching centers.

Technical data

  • Number of access lines: to 250,000
  • Number of feeder lines: 240,000
  • Traffic connection: 25,200
  • Call attempts in busy hour: 10 million
  • Operating voltages: -48V -60V -90V
  • Rate zones: 127, for each zone of 6 tariffs
  • Tariff change-over at 15 minute intervals
  • Space requirement with 10,000 access lines: 35 square meters


  1. ^ Telephone World - Other Modern Switching Systems of Note
  2. ^

External links

This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.