This section discusses telephone switching systems, where phone calls are “switched” meaning they cross through a switching matrix to route calls from an origination point to a destination point. Local “central offices” are where the end users are located. This is the most common switching system in the telephone network. Long Distance “tandem” switches are where long-haul long distance calls are switched to connect local central office switches throughout the world. North American (US/Canada) Vintage (electro-mechanical), Modern (analog and digital electronic) as well as next-generation carrier grade packet-based switching systems are discussed here.
Timeline of Telephone Switch Development
Telephone Switch Timeline
A timeline that shows the development of telephone switching systems up to present day.
Vintage Analog Electro-Mechanical Telephone Switching Systems
Step by Step (Strowger) Switching Systems
Details on the Step by Step (aka Strowger) switching system and its variants.
Western Electric Panel Switching Systems
Details on the Western Electric Panel switching system.
Western Electric Crossbar Switching Systems
Details on the Western Electric Crossbar switching system and its variants.
North Electric Crossbar Switching Systems
Details on the North Electric Crossbar switching system and its variants.
Other Vintage Switching Systems of Note
Details on other vintage switching systems of note that are not mentioned above.
Historic Number 4 Crossbar (#4XB) List
Descriptions and a detailed list of locations where AT&T Long Lines (Bell System) used the Number 4 Crossbar (#4XB) Tandem system in the North American toll network from 1940s until the 1980s.
Modern Electronic & Digital Telephone Switching Systems
Overview & Background of Modern (Electronic & Digital Switching) Systems
An overview, background and history on the different types of electronic (analog) and digital telephone switching systems that are used on the North American telephone network.
Automatic Electric Modern Switching Systems
Details on Automatic Electric electronic & digital switching systems.
Northern Telecom (Nortel) Modern Switching Systems
Details on Northern Telecom (now Nortel) electronic & digital switching systems.
TRW-Vidar Switching Systems
Details on TRW-Vidar switching systems.
Western Electric/Lucent Technologies
Details on Western Electric (later Lucent Technologies) digital switching systems
Other Modern Switching Systems of Note
Details on other digital switching systems of note that are not mentioned above.
Packet Switching – The Next Generation
An overview on carrier grade packet switching (often called “softswitches”) which is the next generation telephone switching system that use Internet routing technologies (often called Voice over IP) to switch and route telephone calls.
Other Telephone Switch Systems websites (off-site)
List of Telephone Switches
Wikipedia article that lists common and not-so common telephone switches of today and yesterday.