Monthly Archives: January 2010

Electrical outlets of the world

South Africa

Switzerland

UK (obsolete)

UK

France

Germany

Italy

Australia

China

North America

Argentina

Top Telephone Switches

With AT&T saying that “with each passing day, more and more communications services migrate to broadband and IP-based services, leaving the public switched telephone network (“PSTN”) and plain-old telephone service (“POTS”) as relics of a by-gone era,” I thought it would be a good time to get a snapshot of the North American telephone network as it exists now. In the early 1970s, phone phreaks like Evan Doorbell and Mark Bernay started recording what they saw as the demise of the electromechanical telephone network. The switches then were crossbars and panels and steps and the like, with early computerized switches like the 1ESS just starting to appear. Now, the 1ESS is nearly gone from the network, and the North American network consists mostly of the Western Electric/AT&T/Lucent/Alcatel 5ESS (the 1ESS’s successor), the Nortel DMS-10 and DMS-100, the GTE Automatic Electric GTD-5 EAX, and the Stromberg-Carlson/Siemens DCO. A few other switches in the network, like the Siemens EWSD and the Ericsson AXE 10 have found more popularity in North America as cellular switches (and as wireline switches in other countries).

The oddball switches are the ones that really interest me, and they’ll be the first ones to disappear from the network. I’ve been told that the TRW Vidar ITS-5 and the Mitel GX5000 switches may be gone from the North American network. To see what might be left, I decided to do some digging, and I’ve come up with a list of the telephone switches (minus remotes) still in use in the North American network. There’s undoubtedly some stale data in this database, and so for rare switches, I think the numbers listed are the upper boundary — the lower boundary may be as low as 0. The list also contains the mystery “Digital Switching System”. There seems to be an awfully large number of them for it to be the North Electric DSS-1, which became the ITT 1210 — maybe it just means “unknown digital switch”?

The picture above of the GTD-5 EAX was shamelessly stolen from the site of a GTD-5 consultant, the only place I could find a picture.

Top 10 Switches

Manufacturer Switch Count
NORTEL DMS 100 2513
LUCENT 5 ESS 2236
NORTEL DMS 10 1968
AUTOMATIC ELECTRIC GTD-5 EAX 668
SIEMENS DCO 522
  DIGITAL SWITCHING SYSTEM 247
REDCOM MDX 384 155
ERICSSON AXE 10 102
SIEMENS EWSD 91
LUCENT 1A ESS 66

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